Higher Neural Functions: A Clinical Approach M Madhusudanan, A Anand Kumar, Arun N Babu
INDEX
Page numbers followed by ‘b’ box; ‘f’ figure; ‘fc’ flowchart; and ‘t’ indicate table respectively.
A
Ability, constructional 171
Abstraction, lack of 96
Abulia 83
assessment of 189
Acalculia 39, 40
Acetylcholine, blockade of 69
Achromatopsia 113, 115
in contralateral inferior quadrant 116f
Acquired amusia, cases of 125
Acquired stuttering 28
Aggression 190
Agnosia 26, 100, 103, 132
apperceptive 103
and associative 101
landmark 120, 120f
material-specific 106
testing severity of 126
treatment of 127
type of 121, 124, 127
Agrammatism 16, 19
Agraphia 25, 33, 36, 37, 39
clinical presentations of 38
in Broca's aphasia 38
in Gerstmann's syndrome 39
in Wernicke's aphasia 38
isolated alexia with 33
lesions causing 31fc
lexical and phonological pathways 31fc
lexical versus sublexical 38
perseverative 40
phonological 38
sublexical 38
Ahylognosia 126
Akinesia 83
type of 159
Akinetic mutism 187, 188, 190
Akinetopsia 138
Alexia 29
anterior 37
clinical presentations of 33
global 20, 32
lesion causing 31fc, 34f
lexical and phonological pathways 31fc
treatment of 37
type of 35
without agraphia 33
Alexithymia 185
Alice in Wonderland syndrome 144
Alien hand syndrome 170
Allesthesia 159, 160
Alternating sequences task 9
Alzheimer's disease 61, 63, 64, 66, 192, 195, 199, 200, 202
Amantadine 144
Amnesia
anterograde 63, 69
functional 63
material-specific 70
neuroanatomy 30
retrograde 63, 67, 69
types of 71t
Amnestic disorder 100
Amorphognosia 126
Amusia 121, 125
congenital 125
Amygdala 59, 60, 179
location of 179f
role of 179
Amygdaloid circuit 59, 60, 60f
Amygdaloid nuclei 179, 180
Analogy 2
Analytic dysfunctions, type of 79
Angular gyrus 13, 163
lesions 25
Anhedonia 189
Anomia 26
Anomic aphasia, disorder of naming 25
Anosodiaphoria 178
Anosognosia 72, 151
Anterior cingulate syndrome 187
Antisaccade test 91
Anton's syndrome 72, 139, 200
Anxiety 192
Anxiety disorders 191
Apathy mutism 187
Apathy, type of 188
abulia 189
akinetic mutism 189
autoactivation 188
cognitive 189
emotional-affective 189
Aphasia 2, 13, 23
bedside testing of 41
conduction 23
diagnosis of 43fc
global 20
in cerebellar dysfunction 24
kind of 42
locations of lesions causing 21f
nominal 109
overview of 13
subcortical 23
Aphasic misnaming 100
Aphemia 25
Apperceptive agnosia 104f
Apperceptive prosopagnosia 113f
Appetite 193
Apraxia 42, 135, 162, 169
cause 164f
conceptual 163, 165
constructional 86, 172
diagnosis of 162
dissociative 167
dressing 169
kind of 165
locations of lesions 169
testing for 171
treatment of 173
type of 165
Aprosodias 29
Arithmetic problem-solving 84, 88
Artificial tests 96
Ascending reticular activation system 6
Asomatognosia, nonverbal 151
Asymbolia 151
Athymormia 188
Attention 6
mediators of 7f
neuroanatomical correlates of 6
neurophysiological correlates of 7
Attentional defects 8
Attentional disorders, treatment of 9
Attentional disturbances 100
Attentional problem 162
Auditory 157
affective agnosia 121, 124
agnosia 120, 122, 123f
types of 121t, 124
hallucinations 203
information 167
verbal agnosia 24
Automatic response 91
Autoscopy 142, 201
Autotopagnosia 151
B
Balint's syndrome 139
Basal forebrain
amnesia 71
damage 69
role of 69
Basal ganglia 38, 66, 70, 188, 196
lesions 169
regions 91
Beautiful mind 177
Bedside memory test 69
Behavior, imitation and utilization 187
Behavioral arousal 155
Behavioral dysfunction, treatment of 205
Behavioral self-regulation 80
Benton facial recognition test 113
Birmingham object recognition battery 109f
Blindness, cortical 72
Blindsight 140
Body, disturbances of 126
Body part apraxia 166
Body schema 151
Brain areas 177f, 179
Brain processes phonemes 11
Broca's aphasia 18, 19, 37
functional neuroanatomy of 20
Broca's areas 12, 21
Brodmann's areas 169
Bupropion 192
C
Callosal apraxia 168
Callosal disconnection syndrome 171
Callosal syndrome 141, 170
Callosotomy 170
Cambridge face memory test 113
Cancellation test 157
Canonical neurons play 165
Capgras syndrome 143, 200
Catastrophe 28
Category-specific visual agnosia 106
Caudate nucleus 155
Caveat 109
Central executive agency 52
Central nervous system infections 195
Cerebellar 135
Cerebellar diseases 66
Cerebellar dysfunction 162
Cerebellum and basal ganglia 15f
Cerebral achromatopsia 115, 133
Cerebral artery, left middle 20
Cerebral cortex 155, 177
Cerebral damage, particular loci of 37
Cerebral hemisphere 58f
Cerebral infarction 191
Channel functions 3
Charles-Bonnet syndrome 145
Cinematographic vision 138
Cingulate circuit, anterior 82, 188
Cingulate gyrus 94
anterior 184
Cingulate lesions 154
Cingulotomy, anterior 198
Circuit function 81
Classical aphasia syndromes 17
Clinical neuropsychological testing 5
Clock drawing test 86f, 86, 158f
defective abstraction for “ten past eleven” 87f
defective planning and organization 173f
defective planning and organization 87f
inability to shift response 87f
left-sided neglect 172f
preservation 87f
Closed-class words 11
Cognition 79
clinical characteristics 82
Cognitive deficit, nature of 97
Cognitive disorders 79
testing for 97
treatment of 97
Cognitive functions 5
Cognitive tasks 61
Cognitive thinking 96
Color agnosia 115, 116, 117t
Color amnesia 117, 117t
Color anomia 117t
Color blindness 115, 117t
Communication, means of 11
Comprehension deficit 162
Concentration 9
Conceptualization 12
Conduction aphasia, neuroanatomy of 23
Coprographia 40
Cornus ammonis subfields 57
Correct pronunciation 30
Cortical vision screening test 108
Corticobasal degeneration 66
Cortico-striato-nigral-collicular pathway 155, 197
Craniopharyngiomas 190
Cushing's disease 192
D
Dawing test, case of left-sided neglect 156f
De Clerambault's syndrome 201
Declarative memory, neuroanatomy of 57f
Deep agraphia continuum 36
Deep alexia 36
Deep temporal white matter 24
Defective working memory 74
Deficit, level of 107
Degenerative extrapyramidal system diseases 200
Delayed response task 8
Delirium 18, 200
Delusional phantom boarder 201
Delusions 199, 200, 200b
examples of 201t
Dementia, type of 75
Dementing diseases 195, 200
Dentate gyrus 57
Depersonalization 201
Depression 74, 193, 195b
experiential manifestations of 194
psychotic states of 97
Depressive disorders 193
Depressive symptoms 193, 194
Derealization syndrome 201
Design fluency test 94f
Diencephalic amnesia 71
Diencephalic damage 69
Digit span test 72
Diminished verbal fluency 93
Disorders of body schema
bilateral 126
unilateral 126
Dopamine agonists 144, 145
Dopaminergic drugs 160
Dopaminergic function 202
Dysarthria 27, 28
Dyslexias 13
Dyspraxic disorders 37
Dysprosody 28
E
Echographia 40
Echolalia 22
Egocentric coordinates 152
Egocentric disorientation 120
Ekbom syndrome 201
Electroconvulsive therapy 194
Emotion
and cognition 84f
and neurobehavioral disorders 175
areas involved in 183
Emotional
and behavioral dysfunction 5
battery testing 205
cognition 205
aspects of emotional cognition 177f
dysfunction 177
communication 11
disorders, neurological basis of 191
dysfunction 177
symptoms of 184
testing for 204
enhancement of memories 62
evaluation 204
expression 177, 205
functions 185, 185t
incontinence 191
lability 190, 191, 191t
memory 60f
perception test 29, 124
processing 176
thinking 97
Encephalitis 192
Encephalopathy, post-traumatic 200
Encoding
and consolidation 57
lays 49
memory 50
mild problem in 74
Endocrine disorders 195
Endocrine function 193
Energization 80
circuit 82
Entomopia 142
Environmental dependency syndrome 187
Environmental sound agnosia 121, 124
Epicenter 3
Epilepsy 192
case of 3
Epileptic psychoses 201
Episodic memory 53, 54, 55
formation, process of 56
impaired
encoding and retrieval of 71
retention of 71
symptoms of 63
neuroanatomy of 56
physiology of 56
symptoms of 56
system 66
Error correction, lack of 187
Euphoria 190
Excitatory control 8
Excitatory failure 8
Executive control network 82
Executive functions 80, 84
Executive network activation 59
Extrapyramidal disorders 66, 195
F
Facial discrimination, impaired 114
Facial emotions 114f
impaired recognition of 114
Facial expressions 29
Facial imagery 112
Facial intermetamorphosis 142
Facial percept 111
Facial recognition 111f, 112f
Facilitatory paratonia 97
Feeling states 82
Finger agnosia 39f, 41f
Fixation, spasm of 139
Fluoxetine 192
Focal brain damage 36
Focal seizures 143
Foreign accent syndrome 28
Formication hallucination 204
Formulation 12
Fortification spectra 144
Foveal optic ataxia 136
Freeze-frame manner 138
Fregoli syndrome 200, 201
Frontal cortex, dorsolateral 185
Frontal degenerative disorders 196
Frontal lobe 81
circuits 81t
dysfunction, physical signs of 97
Frontal poles, role of 183
Frontal premotor region 38
Frontal regions, dorsolateral 80
Frontal simultanagnosia 119
Frontotemporal dementia 195
Fugue states 198
Fusiform face area 64
Fusiform gyrus 13, 30, 111
G
Gaze paresis 159
Gaze, psychic paralysis of 139
Gene expression 62
General auditory agnosia 121, 122
Geniculoextrastriate pathways 140
Gerstmann's syndrome 21
Geschwind syndrome 180
Gestural comprehension, loss of 164
Gesture imitation 171
Gesture perception 171
Gesture production 171
Glasgow face matching test 112
Globus pallidus 81
Gnosis 101f
Gorham proverb test 96
Grandiose delusions 199
Grapheme-phoneme correspondence 35
Graphemes 13
Gustatory hallucinations 203
H
Hallucination 203
haptic 204
type of 201
Headaches 144
Hearing loss, unilateral 157
Hemiachromatopsia, unilateral 116f
Hemiakinesia 152
Hemiasomatognosia 126
Hemiparesis 159
denial of 200
right 20
Hemiplegia, right 2
Hemispace, left 151
Hemispatial akinesia 153
Hemisphere, left 116
Hemispheric dominance 15
Hemispheric lesions, right-sided 160
Hemorrhagic leukoencephalitis 191
Herpes simplex encephalitis 191
Higher neural functions 1, 79
approach to understanding 1
clinical evaluation of 4
examination 5
testing for 4
types of 3
Hippocampal system 50
Hippocampal-entorhinal complex 58
Homonymous hemianopia, right 116
Human development, course of 11
Human selective voice area 111
Human speech sounds 123
Hungarian physician 139
Huntington's disease 192, 195, 196, 197, 200
Hyperkinetic agraphia 40
Hypermetamorphosis 180
Hyperorality 187
Hyperthyroidism 192, 195
Hypnagogic 145
Hypnagogic hallucinations 146
Hypnopompic 145
Hypoglycemia 192
Hypokinesia 159
Hypothalamus 82, 177
Hypothyroidism 195
Hypoxia 192
I
Ideomotor apraxia 164, 165, 166, 169
presence of 166
steps in testing for 166
Ideomotor limb apraxia 167
Idiopathic basal ganglia calcification 195, 196
Imageability 30
Impulsive hypothesis 119
Inability to organize and plan 84
Indiscriminate eating 187
Inferolateral prefrontal 63
Inferotemporal region, posterior 38
Inhibitory control 8
Insula 60
Insular cortex 38
Insular cortex, role of 183
Intact sensory function 162
Intelligence 96
Interhemispheric disconnection 3
Interhemispheric disconnection, disturbances related to 141
Internal vocabulary 36
Intoxication 74
Intuition 96, 97
Irritability 82
Isoniazid 192
Isthmus 6
J
Jargon speech 16
K
Kinesthetic reading treatment 37
Kluver–Bucy syndrome 180, 190, 198
Koro syndrome 201
Korsakoff's syndrome 67
L
Landau–Kleffner syndrome 24, 125
Language 5, 11
components of 29
disorders, treatment of 43
dysfunction 17f
symptoms of 16
types of 15
function 2, 15
major brain areas for 21f
neuroanatomy of 11
processing, basic concept of 17f
Lesions, sites of 53
Letter fluency test 93b
Letter-by-letter readers 32, 33
Levodopa 144, 145, 192
Lewy body disease 144
Lexicalization 35
Libido 193
Limbic circuit, basolateral 59
Limbic motor cortex 181
Limbic structures 191
Limbic system 57, 202
role of 179
Limb-kinetic apraxia 167
Line bisection test 157, 157f
Lingual and fusiform gyri 115
Lingual gyrus, anterior 120
Linguistic alexias 35
Lissauer's classical work 103
London, tower of 86
Luria three-step alternating sequential motor test 92
M
Macropsia 142
Macrosomatognosia 151
Major aphasia syndromes 23t
Mammillothalamic tract 56, 59
Manganese intoxication 197
Mania 74, 82, 194, 196b, 196,
Medial temporal lobe, role of 66
Melodic stress 29
Memory 5, 49
categorization of 54fc
classification and duration of 51t
classification of 50
contextual 55
different types of 66f
disorders 72
distortions 72
dysfunction
clinical manifestations of 69
treatment of 74
encoding and consolidation 61f
examples of 54
function, test 50
impairment 69
landmark navigation and topographical 62
long-term 53
types of 53
loss 69t
pathophysiology of 66
nature of 50, 54
nondeclarative 65, 65f
types of 65
nonverbal 74
of future 85
procedural 50, 54, 65
recent 73
remote 6162, 74
retrieval errors 63
spatial 62
stage of 70, 70t
storage of 62
testing 72
type of 51, 54, 54t
Mental deterioration 100
Mental emptiness 188
Mentally sedentary 83
Mesencephalic reticular lesions, unilateral 155
Mesial temporal area 139
Metacognitive processes 82
Metamemory 68
Metamorphopsia 142
Micrographia 40
Microplanning 12
Micropsia 142
Microsomatognosia 151
Midbrain nuclei mediate 176
Migraine 192
Migraine auras 143
part of 115
Mind-healthy techniques 97
Modality-specific aphasia syndromes 24
Modularity 3
Monoamine oxidase type B 144
Morphology, synaptic 62
Motivation 184
Motivational neglect, type of 154
Motivational state 7
Motor aphasias 15
Motor aprosodia 29, 178
Motor bias rehabilitation 160
Motor component 150
Motor coordination disorder 167
Motor cortex, primary 162
Motor cortices 177
Motor extinction 159
Motor hyperactivity 187
Motor impersistence 160
Motor memory 85
Motor programming tasks 92
Movement
lack of 189
types 162
Musical instrument 66
Mutism 83
N
Naming 42
components of 26
Neglect
components of 150
intentional component of 152
perceptual 156
testing for 156
unilateral 153
Neglect syndromes 141, 149, 150, 159, 190, 200
clinical presentation 155
test for 156
treatment 160
Neighborhood signs 4
Neologistic paraphasia 16
Neural function, components of 3
Neuroacanthocytosis 196, 197
Neurobehavioral disorders 83, 79
Neurobiochemical level 202
Neurocognitive, basic physiology of 79
Neurocognitive disorders 79, 83
Neurological and medical disorders 192
Neurological and psychiatric disorders 143
Neurological diseases 185t, 195b
differentiating delusions of 202
Neurological disorders 197b
Neurological functions 3
Neurological illnesses 194
Neuronal circuits 191
Neurons 132
Neuropathology 122
Neuropsychological 102
Neuropsychological models 101f
of apraxia 163
of visual object recognition 132
Neuropsychologists 96
Neurosyphilis 196
Neurotransmitters act on cells 1
Nonlinguistic agraphia, types of 40t
Novelty detection 94
Novelty in stimuli, recognition of 95f
Nucleus accumbens 190
Nucleus reticularis thalami 155
O
Obsessive-compulsive disorder 82, 196, 197b, 197
Obstructive hydrocephalus 190
Occipital face area 111
Occipital lobe 115
Occipitotemporal cortex 21
Occupational therapy 146
Oculomotor apraxia 139
anatomy of 140f
Olfactory hallucinations 203
Optic aphasia 107, 108
Optic ataxia 134, 135, 137f, 138, 139
anatomy of 136f
mechanism 135
Optic nerve, pathology 115
Optokinetic stimulation 160
Orbitofrontal
and cingulate 176
areas 198
circuit 181
cortex 60, 83,182
hyperactivity 196
lesions 181, 196
Orbitofrontal syndrome 190
Organic brain disease 203
Organic catatonic disorder 199
Orientation 9
Orofacial apraxia 167, 168
Orthographic agraphia 39
Orthographic lexicon 36
Oscillator, primary 3
Othello syndrome 201
P
Pain hallucination 204
Paligraphia 40
Palinopsia 142
Panic attack 192
Panic disorder 192
Paper and pencil tasks 153
Papez circuit 59f, 59, 67
part of 74
Paragrammatism 16
Parahippocampal areas 67
Parahippocampal gyri 6, 120
right posterior 120
Parahippocampal place area 64
Paraolfactory gyrus 60
Paraphasias 16
Paraphasic errors 25
Parietal agraphia 38
Parietal cortex 68
Parietal neurons 7
Parieto-occipital area 135
Parieto-occipital junction 38
Parietotemporal lesions, right 120
Parkinson's disease 66, 144, 145, 189, 192, 195, 196
Partial amnesia 70
Particular brain function 6
Patastrophie 27
Peduncular hallucinations 145
Perceptions, content of 79
Perceptual categorization deficit 104, 105f, 108
Peripheral lesion, unilateral 157
Peripheral motor disorder 13
Peripheral sensory deficit 13
Perirhinal-lateral entorhinal area 58f
Perirolandic regions, cortical disorders of 66
Perisylvian cortical areas 36
Perseveration 91
Person identity node 111
Phonagnosia 121, 124
presence of 124
Phonological alexia 35
features of 35
Phonological deep alexia 36
Phonological lexicon 132
Phonological processing 32, 32f
Picture sign 201
Placement test 97
Polyopia 142
Polysyllabic words, production of 27
Pontine lesions 203
Porteus Maze test 85, 86f
Postencephalitic parkinsonism 196, 197
Postencephalitic syndromes 196
Praxicon 162
Praxis
disorders of 5
model of 163
simplified model of 164f
Prefrontal circuit, dorsolateral 81
Prefrontal cortex
appear 52
dorsolateral 12
role of 180
superomedial 188
Prefrontal lobes
dorsolateral 94
role of 68
Prefrontal structures, dorsolateral 52
Prefrontal-subcortical circuits 80f
Primary motor cortex, right 162
Primary motor disorder, causing weakness 162
Priming 65
Problem-solving and creativity 94
Prosody 29
Prosopagnosia 101, 106, 109, 110
causes of 113
conditions related to 114
locations of lesions causing 112
pathophysiology of 111
testing for 113
Prosopagnosticon 110f, 110
Prosopometamorphopsia 142
Prosopon means face 101
Protein synthesis 62
Proverb interpretation test 96
Pseudodementia from dementia 195t
Pseudodepressed personality 83
Pseudonym 36
Pseudopsychopathic behavior 83
Psychiatric disability 198
Psychiatric diseases, primary 202
Psychiatric presentations 83
Psychic akinesia 188
Psycholinguistic syndromes 37
Psychopharmacological agents 194
Psychosis 202
Pure alexia 32, 33
Pure anarithmetria 41
Pure word deafness 24, 121, 123
R
Raise your left hand 43
Reading 43
aloud 43
comprehension 43
disorder of 13, 24, 29
errors 35
Real-life behavior 96
Reduplicative disorder 143
Reduplicative paramnesia 201
Reflect nervousness 74
Registration 56
Repetition 42
disorder of 27
Reticular activation system 145
ascending 155
Retinotectopulvinoextrastriate 140
Retinotopic information 134
Rey, complex figure of 87, 88f
Rey–Osterrieth design, modified 88f
Ribot's law 63
Riddoch syndrome 141
S
Schizoid 185
Schizophrenia 74, 97
Sclerosis, multiple 192, 195, 196, 200
Seelenblindheit 100
Seizures 144
Semantic 11
agraphia 39
alexia 35
category fluency testing 64
memory 50, 54, 63
disorders of 64
impaired 71
part of 53
network activation 59
processing 32, 32f
disorder of 35
system 107
Sensory
aphasias 15
aprosodia 29, 121, 194
data, transmission of 155
dysfunction 162
information 155
neglect 157
stimuli 175
Sentences, structure of 12
Septal area 198
Septal nucleus, medial 69
Serotonergic antidepressants 198
Sexuality, altered 198
Simple persecutory delusions 199
Simultanagnosia 118, 119, 139
dorsal 118
due to frontal lesions 119
test for 118f
Single word comprehension deficits 17
Social cognition 184
circuitry involved in 185fc
Somatoparaphrenia 151
Somatosensory dysfunction 135
Soul blindness 100
Sounds, types of 120
Spacicon 154f
causing neglect 154f
Spatial information 57
Spatial neglect 157
disorders of 5
Spatial relations 126
Spatial-temporal movement representations 163
Speech
apraxia 19, 27, 28
articulation, disorders of 27
comprehension, schematic pathway for 14f
disorder 24
expressive 41
fluency, disorder of 25
Splenium 33
Spoken language, comprehension of 42
Spontaneous writing 24
State functions 3
Statokinetic dissociation 141
Stereopsis and depth perception, loss of 137
Stimuli
changing 88
significance of 179
Story recall 74
Stress, role of 204
Striatal subcortical aphasia
anterior 24
posterior 24
Striatum 81
Stroke 192
and vascular dementia 195
Stroop interference test 9, 91f, 91
Supplementary motor area 13, 162
Supramarginal gyrus 21, 163
Supranuclear palsy, progressive 196, 197
Surface alexia 35
Sydenham's chorea 196, 197
Symbolic representations, stages of 102
Symptomatology 52
Syndrome of doubles 201
Syndrome of intermetamorphosis 201
Syndrome of spatial neglect 8
Systemic lupus erythematosus 195
T
Tactile agnosia 126
Tactile asymbolia 126
Target cancellation test, case of left-sided neglect 158f
Target's visual coordinates 135
Task-specific apraxia 168
Teichopsia 144
Telegraphic 19
Telegraphic speech 19
Temporal amnesia, medial 71
Temporal cortex, anterior 110
Temporal gyrus, superior 12
Temporal lobe 25, 26
anterior, role of 182
bilateral 185
epilepsy 200
seizure aura 203
structures, medial 59
Temporal poles 60
lesions of 182
Temporooccipital cortex 33
Temporoparietal cortex, left 36
Temporoparieto-occipital junction 21139
Temporopolar regions 63
Texting 11
Thalamic aphasia 24
Thalamic nuclei 81
Thalamic reticular nucleus 8
Thalamotomy, sequelae of 196
Thalamus 38
medial 190
Thought 36
and action, impulsivity of 186
Three loop test, example for 93f
Thyroid hormones 192
Timestamp 58
Token test 42
Tongue phenomenon, tip of 19
Topographagnosia 113, 119
Topographical amnesia 70
Tourette's disorder 196, 197
Trail making test 90, 90f
Transcortical aphasias 20, 22
motor 20, 21
sensory 21
Transitory syndrome 25
Trauma 192
Tricyclic antidepressants 192
Tuberoinfundibular region 198
U
Uncinate fasciculus 196
Upper limb motor disorders 37
V
Vascular dementia 199, 200
Ventral
compartment 193
globus pallidus 190
pallidum 189
pathway damage 133
simultanagnosia 118
striatum 189, 190
Verbal
asomatognosia 151
auditory agnosia 121, 123
comprehension 18
disorder of 24
dissociative apraxia 168
emotional perception 205
fluency 84
stimuli 121
Viral encephalitis syndrome 195, 196
Visceral afferents 82
Visceroautonomic 82
Vision loss 157
Visual 157
agnosia 2, 103f, 168, 120
assessment of 103
general 101
mild 106f, 109f
neuropsychological batteries for 108
specific types of 109
testing for 107
severity of 108
allesthesia 142
amnesia 143
and auditory perception, disorders of 5
apperceptive agnosia 104f
association cortex 2
attention
competing for 150
lack of 133
cortex 140
disorientation 133, 134, 138
mechanism 134
tests 134
dissociative apraxia 167, 168
field defects 135, 144
gnosticon 117, 117f
hallucinations 141, 143, 144, 145, 203
type of 142
hypoemotionality 143, 180
illusions 142t
types of 142
imagery 111
inattention 138
information 26, 29
memory 73
object agnosia 103
orthographic processing 30
pathway 141
pattern completion test 92f
perception, impaired 26
phobias 143
processing
ability 93
higher 102f
pathway for 58f
recognition, models of 102
synesthesia 142
target cancellation tasks 153
word-form area 13
Visuoimitative apraxia 168
Visuomotor coordination 135
Visuospatial agnosia 40, 135
Visuospatial disorders 133
Visuospatial dysfunction 169
Visuospatial information 52
Visuospatial problem-solving 84
Visuospatial working memory 73, 155
Vitamin B12 deficiency 201
Vocabulary 30, 107
Volitional action system 193
Voluntaryautomatic dissociation 166
W
Warrington's recognition memory test for faces 113
Waxy flexibility 97
Wernicke's aphasia 18, 19, 120
functional neuroanatomy of 18
Wernicke's area 2, 12, 21
White matter
subcortical 25
underlying 21
Wilson's disease 66, 192, 195, 196, 200
Wisconsin card sorting test 89, 89f
Withdrawal states 203
Word
collection of 30
list generation 93
pathway for comprehension of 14f
Working memory 51, 54, 72, 73
function 51
phonological loop 52f
physiology 51
visuospatial sketchpad 52f
Writing 43
disorder of 25, 37
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Chapter Notes

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Approach to Understanding Higher Neural Functions1

 
INTRODUCTION
Higher neural functions comprise sensory perception, motor perception, language, memory and learning, gnosis, praxis, emotions, behavior, executive thought, planning, and insight (including our attempts to gain insight into how we perform these very functions, which is the subject of this book). Our study of these functions go to the very core of trying to understand who we are as individuals and ultimately, as a species. The branch of psychology and neurology that studies how the structure and function of the brain relate to specific behavioral, emotional, and cognitive processes is termed neuropsychology.
The workings of the brain in higher functions have remained an enduring mystery of science. This book attempts to describe what is currently known about how the human brain performs higher mental functions at an organizational level, and how this helps us to understand how particular symptoms or signs may suggest certain types of pathology in specific brain regions, thus providing information that may be helpful clinically. The discussions of what is known about normal functioning will be geared to this purpose. We know that brain functions are subserved by multiple interacting networks for any given function. A new experience activates a group of neurons and as the slogan goes “neurons that fire together wire together”, resulting in new connections and eventually, a new circuit in the network. A network generally has a governor or a primary oscillator that orchestrates the system along with numerous other components that may be scattered in different brain areas.
It should be appreciated, however, that the true functioning of the brain in performing its remarkable tasks is actually far more complicated. Neurons generally communicate through synapses using neurotransmitters. Neurotransmitters act on cells through receptors and ion channels, resulting in electrical changes. Electrical changes can translate to intracellular signal transduction and gene activation. Genetic and environmental factors influence these processes. Indeed, other physical and chemical factors, about which we currently have little knowledge, also likely play an important roles.
A lot of work has gone into demonstrating many of the subcellular mechanisms involved in these processes. However, we still have little insight into how the molecular and genetic mechanisms actually result in the subjective conscious experience we appreciate as humans.
Adding to the difficulty in elucidating these phenomena is the fact that some functions, like sensory perception, occur as a highly-individualized subjective experience that may vary from human to human. We simply have no way of testing whether what one person feels when looking at a red bird is the same as what someone else feels. Subjective experience is clearly deeply intertwined with a person's previous experience, current emotional and motivational state and other mental activity, genetic makeup, and possibly, 2other random individual factors such that each person's perception of something is probably a unique event in the universe.
Most of our current understanding of normal higher functions has come from observing what happens when things go wrong, carefully documenting the symptoms and signs and natural course of various disease states, and trying to correlate it with findings (lesions) on pathologic examinations and neuroimaging. This, however, has its pitfalls as lesions do not necessarily correlate directly with functional anatomy. For example, the ancient Egyptians may have observed that when a soldier is stabbed in the neck, lacerating the left carotid artery, he develops a right hemiplegia and aphasia. This could have led to a conclusion that right-sided movement and language functions were mediated by the carotid artery. Today, we know that is far from the whole story. Finding that a particular deficit is associated with a focal lesion in a part of the brain does not mean that the function is subserved by that area. It only means that injury to that area can somehow result in a failure to be able to perform that particular function and that the area likely plays some role in the performance of that function.
We know today that the brain performs many of these higher functions through simultaneous activity in multimodal neural networks that involve multiple areas in the brain. Therefore, how then does a focal lesion, such as a stroke affecting Wernicke's area, result in a loss of verbal comprehension? The answer appears to be that while comprehension is a function that is mediated simultaneously through multiple neural networks involving widespread regions of the brain, a focal lesion in any of these widespread areas may disrupt some of these networks, but this may not be enough to cause an obvious deficit in comprehension on a bedside examination. However, as most of these networks pass through Wernicke's area, damage to this area disrupts such a large number of networks that the breakdown in comprehension function becomes glaringly apparent.
An analogy is what happens if there is a power failure at a city's telephone exchange. This may result in a total breakdown of all telephone communications and there would not be even a single telephone call taking place in the city. It would be wrong to simplistically assume, this meant that all telephone calls normally emanate from someone sitting in the telephone exchange. The telephone exchange is simply an important relay station or hub in the widespread mediation of this function.
We also understand that the brain appears to perform some complex functions by breaking them down into more basic components, processing them simultaneously, and somehow binding together the result and perceiving it in its entirety. For example, when we see a red bird flying fast, some neural networks process the shape, others the color, some networks process the location in the visual field, and still others code for the motion. Lesions in individual places may produce isolated deficits in one or more components. Lesions in the visual association cortex, where most of these networks converge, may disrupt most of these networks, resulting in more profound damage and a fullblown “visual agnosia”. Sometimes, lesions may occur in nodal areas, where many of these networks converge (such as Wernicke's area or the angular gyrus in the case of language) and this may produce total disruption of the function due to the large number of networks that have been rendered inoperable. When the lesion occurs in between nodal areas, such as in the parietal white matter, some networks 3may be damaged but the overall functional implications will be less severe. When lesions disrupt fibers within the same hemisphere, it is referred to as “intrahemispheric disconnection”. When connections are disrupted between the two hemispheres, it is called “interhemispheric disconnection”.
In essence, when studying a neurological disorder, it is clear that there are many different aspects that have to be kept in mind.
 
Components of Neural Function
The components of neural function are discussed below:
  • Epicenter: Most disorders may have a primary area of initial dysfunction. This can be referred to as the “epicenter” of the disorder. While taking a history, it is essential to accurately define the onset of the disorder as the initial presentation will give the best indication of the site of the epicenter of pathology.
  • Networks: Neurological functions, as described earlier, generally involve activity in multiple networks. In any neurological disorder, symptoms will occur based on the “networks” or units of networks, called “connectomes” that are disrupted.
  • Modularity: Complex functions usually involve multiple simpler components. The brain performs complex functions by performing individual component functions simultaneously and binding the result. A set of brain areas and their networks that perform a basic function can be referred to as a “module”. When a module is rendered dysfunctional, all activities performed by that particular module may be affected.
  • Primary oscillator: Neural networks may generally have a primary oscillator that directs activity in the network. Damage to the primary oscillator (such as a lesion in Wernicke's area) causes more damage than damage to other parts of the network (such as a transcortical lesion).
 
Types of Higher Neural Functions
There are essentially two types of higher neural functions.
  1. The first are the “state functions” that maintain the state of activity of the brain as a whole, such as level of arousal, attention, and mood. These are largely maintained by the ascending reticular activating system and networks involving the frontal and parietal areas and limbic system. These functions are usually affected by metabolic or toxic disorders of a diffuse nature, and less commonly, by focal lesions of the concerned areas.
  2. The other set of functions are the more task-specific functions such as visual perception, auditory perception, language, and memory. These functions are also mediated by diverse interacting networks as described earlier. However, based on studies of pathologic dysfunction, we have been able to identify specific channels or pathways in the brain where lesions appear to cause a major disruption in the particular networks mediating these individual functions. These functions were, therefore, referred to in the past as “channel functions”.1 As a result, clinically, deficits in these functions are often helpful in localizing the site of brain pathology.
Higher mental functions, like other physiologic functions, can be affected by a wide range of disease states. Dysfunction can occur as a result of hypofunction or loss of function in one or more modalities. It can also occur as a result of hyperfunction (as in the case of epilepsy).
Dysfunction can occur at the network, cellular, subcellular, electrical, proteomic, or genetic level.4
 
Future Considerations
In the future, as our knowledge of underlying brain mechanisms grow, we may confront additional questions, regarding:
  • The network involved?
  • The neurotransmitter basis?
  • The receptor basis?
  • The electrical dysfunction?
  • The genetic basis?
 
CLINICAL EVALUATION OF HIGHER NEURAL FUNCTIONS
 
Basic Principles
In general, clinical evaluation and management of higher neural dysfunction follows the same rules and guidelines as in other systems.
  • The first question is to assess whether abnormal symptoms or signs are present. As discussed earlier, this may require careful consideration of multiple factors that may influence a patient's performance on neuropsychological and cognitive examinations.
  • The next step is to consider all the known sites of pathology that may result in the manifest symptoms or signs. Sometimes, the “site” might also be the whole brain as in the case of metabolic disorders.
  • Next, we try to rule out or exonerate as many of these suspects as possible, based on the presence or absence of other symptoms “or neighborhood signs” that would be expected with lesions in some of these sites.
  • Having identified the site of dysfunction, we try to identify the etiology. The temporal profile of symptoms usually plays a central role here. For example, with memory loss, an abrupt onset suggests trauma or a stroke. A gradual, chronic course suggests a degenerative disorder like dementia.
  • Armed with an etiologic diagnosis, the next step is to try and make a more definitive pathologic diagnosis, e.g., identifying the particular organism that might be involved in a case of encephalitis. Neuroimaging or laboratory testing is usually involved.
 
Testing Higher Neural Functions
Results of tests of higher neural functions need to be interpreted prudently, keeping in mind the entire picture, and tests may need to be modified and adapted to tailor to individual clinical situations.
Several factors can influence test results.
  • One complicating factor in assessing higher functions is that most of them are necessary contributors to the performance of each other. If a patient has poor attention, he may perform poorly on a memory test, but this may not truly be due to a defect in memory function itself. It may simply be from the poor attention. Clinically, this distinction can be made by observing that the patient does poorly on all functions that require attention, not just memory alone. The examiner needs to be alert to these potentially confounding factors in the interplay among the different elements of higher function testing.
  • Many factors, such as age, gender, education, cultural and language backgrounds, and medications, can influence test performance. It is virtually impossible to collect normative data for all these variables. It may also be necessary to improvise tests for unusual symptoms depending upon a patient's education, interest, and occupation.
  • Motivation and interest are other factors. A happy and interested patient may perform better than the one who is very depressed and has no interest in what is going on. These factors need to be considered while interpreting test results.5
  • Many aspects of human behavior cannot be objectively tested such as insight, motivation, foresight, compassion, or many aspects of problem-solving ability.
  • Not all test results are equally easy to interpret. Calling a toothbrush a “truthcrush” or failing to identify an object by vision but not by palpation can be easily interpreted as abnormal and does not need to be compared to normative standards. However, a failure to name items only at the upper levels of difficulty may simply reflect a lack of vocabulary or infrequent usage of the item which the patient was asked to name.
 
Clinical Neuropsychological Testing
Given the broad range of higher neural functions, tests to assess these functions are often laborious and time consuming. Formal testing using a fixed battery of neuropsychological tests, such as the Halstead–Reitan neuropsychological test battery,2 may take anywhere from 90 minutes to 6 hours, which is impractical at the bedside. Traditional neuropsychological reports can be up to 10 pages long, filled with a variety of tests and scores, often with a liberal amount of technical jargon that may be unfamiliar to clinicians other than dedicated neuropsychologists.
What is ideal is a concise and focused evaluation which will provide the most meaningful and clinically relevant information to help the referring physician arrive at a diagnosis and help in the management of the patient.
 
HIGHER NEURAL FUNCTION EXAMINATION
  • Attention, orientation, and concentration: The examination should begin with an assessment of attention including level of arousal and motivation since primary deficits in these state dependent functions will influence test selection and also interpretation. Then, one should test for orientation and ability for concentration.
  • Language: Next, language is tested as deficits in language may compromise most of the following testing.
  • Memory: Explicit memory is tested next, using both verbal and nonverbal materials.
  • Cognitive functions: Executive functions, reasoning, judgment, and insight can be assessed based on direct testing as well as historical information about the patient's daily living activities
  • Disorders of visual and auditory perception: Any indication of abnormal visual and auditory perceptual functions should prompt detailed testing to localize and diagnose-related disorders.
  • Disorders of spatial neglect: Any spatial neglect syndrome should be excluded.
  • Disorders of praxis: Inability to perform skilled motor acts in the absence of any motor deficit should prompt testing for apraxia.
  • Emotional and behavioral dysfunction: History is critical in behavioral dysfunction as objective tests are lacking.
A more detailed description of mental status testing is given at the end of the last chapter.
REFERENCES
  1. Mesulam MM. Large-scale neurocognitive networks and distributed processing for attention, language, and memory. Ann Neurol. 1990;28(5):597–613.
  1. Reitan RM, Wolson D. Halstead–Reitan neuropsychological test battery. Tucson, Arizona: Neuropsychological Press;  1985.