Lesson 11

Cerebral Cortex - Ch 19, Ch 2 (p. 66-70), Ch 16 (p. 323-326)

what is neurology

study of diseases that affect the nervous system

what is electroencephalography

electrical study of neuronal firing patterns in the brain

• has poor localization abilities than CT and MRI

can be usedd on awake patient as guide for excision of brain matter —> helpful for speech and langauge areas of brain

what are the types of divisions of the cortex of the brain

• primary motor areas

• primary sensory areas

• association areas

what are the 2 types of association cortices

• unimodal association cortices (ex. visual, auditory)

• heteromoda; association cortices: sensory association areas for interatcion of senses, prefrontal cortex for executive functionig etc.

what is executive functioning

the process that decides which of the many incoming sensory stimuli should receive attention, which responses or motor outputs should be activated, and in which sequence

what is the precentral gyrus for, where is it, brodmann area

The primary motor cortex

• in frontal lobe

• represents contralateral side of body in a map —> homunculus

• Brodmann area 4

• produces contractions of specific sets of muscles or speccific movements

how is the homunculus represented in the motor cortex

more area designated to parts of body with higher neuronal concentration and importance of fine movements (i.e. face, lips, hands)

• face and lips are on the inferior (lower) part of the gyrus (just above the Sylvian fissure) —> hands and arms are above the area for face and lips —> legs and foot on superior part of gyrus and extend into the medial aspect of the hemisphere

what part of the frontal cortex is found just anterior to the primary motor cortex, what does it do, what is brodman area

the premotor cortex

• involved in initiation and planning of skilled motor movements

• BA 6

what is the Broca’s area for, where is it, brodmann area

for programming patterned movements of vocal apparatus to produce phonemes and words

• found just anterior to the motor cortex region dedicated to face muscles (makes sense for innervating those muscles for speech)

• BA 44 and possibly 45

What happens from damage to Broca’s area

Broca’s Aphasia: nonfluent speech, partially preserved comprehension

What is Brodmann area 8 + where is it

in superior frontal lobe —> anterior to the premotor cortex

• for movement of eyes and head to contralateral side

What is the supplementary motor cortex for, where is it, brodmann area

on the medial side of the frontal lobe hemisphere —> anterior to leg area of primary motor cortex

• For producing complex postures or patterned movements

• necessary for initiation of speech

• BA 6

what is the dorsolateral prefrontal cortex for, where is it, brodmann area

• it’s a frontal heteromodal association cortex

• for executive functioning, working memory

• BA 9 and 46

what is working memory

combining immeidate memory with cognitive processing

where is the prefrontal cortex located

anterior to the premotor area and the orbitofrontal cortex

what does lesion to prefrontal cortex produce

frontal lobe syndrome: disinhibition of speech and other behaviours

what happens from lesions of orbitorfrontal cortex (i.e. underside of prefrontral cortex —> right behind eyes)

normal intelligence and memory BUT totally changed personality (short temper, irritability, poor impulse control, sociopathic personality

what is akinetic mutism/abulia

reduction or cessation of behaviour due to biliateral lesions to the oribitofrontal area

• i.e.e patients sit and stare passively without speaking → AKA pseudodepressed

what is the general description of frontal lobe syndromes

• they resemble psychiatric disorders since they involve profound alterations of behaviour and personality, yet basic cognitive functions and motor and sensory functions remain intact

what is the cingulate gyrus for, where is it

on medial surface of brain —> a gyrus/fold in the brain that is located above the corpus callosum

• this gyrus is part of limbic system

• circuit goes as folloes: projections from hippocampus, to anterior thalamic nuclei, to cingulate gyrus, back to hippocampus

• for memory and elementary limbic functions (motivation, drive)

what are the 3 parts of the parietal lobe

the anterior portion, superior lobule, inferior lobule

what is in the anterior part of the parietal lobe

Brodmann areas 3, 1, 2 —> for sensory function

what is in the inferior parietal lobule

Brodmann areas 39 and 40 = angular and supramaringinal gyri

what is the inferior parietal lobule in the left hemisphere for

language function —> reading, writing, naming, calculations, and arithmetic

• it’s part of the heteromodal association cortex

what are the 4 deficits associated with lesions of the left inferior parietal lobule

agraphia, acalculia, right-left confusion, finger agnosia (loss of ability to know which fingre is which)

what is the inferior parietal lobule in the right hemisphere for

body schema

what are the superior parts of the parietal cortex for

visuospatial and constrictional functions (i,e, drawing a clock, copying figures) + higher-level cortical sensory functions (i.e. stereognosis and graphesthesia)

what happens with lesions to right parietal lobe

• neglect of left-side of body

• denial of the presence of a motor deficit (anosognosia)

• dressing apraxia (inability t o place garments correctly in relation to body parts

• other spatial and topographical dysfnucions

we know that damage to the left parietal lobe can lead to some language-related deficits like with reading and writing BUT

what happens with lesions to right hemispere in terms of language

lack pragmatic abilities —> emotional intonation of speach is lacking, inability to comprehend emotional tone in speech of others, fail grasping sarcasm/humour, fail turn-taking

• ultimately can lead to personality changes overtime, which are arguably more dificult that certain handicaps like inability to speak

what is in the superior temporal gyrus on each hemisphere of the temporal lobes + Brodmann areas

the primary auditory cortex (BA 41 and 42)

what happens form lesions to primary auditory cortex on both sides

cortical deafness or pure word deafness (inability to undersand spoken words) or auditory agnosia (inability to recognize nonverbal sounds)

where is the Werknicke area located and what does it do

in the left superior temporal gyrus

• for comprehension of spoken language

what happens with lesions to the RIGHT temporal lobe

not much —> it’s kinda a “silent'“ lobe in that it does not lead to many deficits

• does lead to syndromes of confusion or delusional thinking,

• appreciation of rhythm and musical qualities may be impacted

• deficitsof nonverbal memory

what is located within the medial temporal areas

the hippocampus

what structures are for memory

hippocampus, thalamus, septal area, cingulate gyrus

whats the difference between lesions in right temporal lobe vs left medial temporal lesions

right: nonverbal memory loss

left: verbal memory loss

what is in the occipital lobe, what does it do, Brodmann areas

primary visual cortices for vision —> BA 17

what happens with damage to one side of the occipital cortex

contralateral hemianopic visual field defect in both eyes

what happens with damage to both sides of the occipital cortex

cortical blindness

how is vision associaeted with parietal lobe

the dorsal visual pathway cuts through the parietal lobe, which is involved with spatial aspects (the WHERE) of visual perception (note: the ventral visual pathway is for identifying the WHAT of vision —> what they are seeing)

what do the visual association cortex do and what are the brodmann areas

contribute to complex visual analysis —> BA 18 and 19

what is cerebral dominance

since most people are right-handed, the contralateral hemisphere (i,e. the left hemisphere) is dominant on certain things —> LIKE LANGUAGE

• left handed individuals are more likely than right-handed people to have bilateral or right hemisphere language dominance

  • but there are also many left-handed people who are left langauge dominent

what is dysarthria

a motor speech disorder leading to abnormal speech articulation

• involves abnormal strenth or place of articulation, abnormal timing or speed of articulatory movement or abnormal voicing

no impact on comprehension or meaning, just impact on articulation

list the 6 types of dysarthria

flaccid, spastic, ataxic, hypokinetic, hyperkinetic, mixed

what is flaccid dysarthria + cause

hypernasal, breathy speech with imprecisely articulated consonants

due to:

• lesions of bulbar (head/neck) muscles, neuromuscular junction, cranial nerves, and anterior horn cells of brainstem nuclei

What is spastic dysarthria

harsh, strained speach with slow speaking rate + low pitch + imprecise articulation

due to:

• bilateral lesions of motor cortex and corticobulbar tracts (motor tracts of head and neck)

what is unilateral upper motor neuron dysarthria

a type of spastic dysarthria resulting from unilateral lesion —> same cahracteristics as spastic but less severe

What is Ataxic dysarthria + Cause

irregular cadence or prosody of speech with long pauses and sudden explosions of sound, imprecisely articulated consonants —> sometimes over even —> sometimes very slow and exaggerated

• caused by some cerebellar disorders

what is hypokinetic dysarthria

decreased and monotonous loudness and pitch, occasional rushes of syllables, occasional pauses, imprecisely articulated consonants

• associated with parkinsons disease

what is Hyperkinetic dysarthria

variable rate, excessive variation in loudness and timing, distorted vowels

• seen in movement disorders like Huntington disease

what is dystonia

a form of dysarthria —> harsh strain-and -strangle speech with imprecisely articulated consonants

What is Mixed dysarthria

a combination of any of the 5 types of dysarthria

what is apraxia of speech

abnormal articulation of sequences of phonemes, inconsistent error patterns from one attempt to next —> different from dyarthrias in that there is consistent misarticulation

• inability to program sequences of sounds and consonants —> consonants are more often substituted with others —» difficult with initial consonants

• speech is hesitant

• eg. may attempt to say a word like catastrophe many times and failing each time with different errors

**usually apraxia of speech is part of aphasia (esp Broca aphasia)

what is aphasia

an acquired disorder of language functions secondary to brain disease

What is Broca Aphasia

lesion of Broca area in left posterior part of inferior frontal gyrus

nonfluent, halting, dysarthric, ungrammatical speech, minor structural words often excluded, naming deficient

• normal auditory comprehension for the most part

  • difficulties comprejending complex syntax

• reading comprehension impacted

• often accopmanied by agraphia

  • difficulty gripping pen too

What is Wernicke Aphasia

due to lesions from Wernicke’s area in posterior two-thirds of left superior temporal gyrus

fluent effortless speech, obscured meaning of speech, overabundance of stock phrases and idioms and many verbal errors, severely impaired auditory comprehension

• writing is abnormal —> content of writing is similar to content of speech —> abnormal spelling patterns

what is global aphasia

lesion of left middle cerebral artery territory of frontal, temporal, parietal lobes OR large lesions of subcortical white matter and basal ganglia

sum of deficits of Broca and Wernicke aphasias

• nonfluent or mute + impaired comprehension

• severe impairment of all language: speech, naming, comprehension, repetition, reading, writing

what is conduction aphasia

rare

lesion to either inferior parietal lobule (esp supramarginal gyrus) OR an incomplete damage to Wernicke area

repetition is most severely affected

spontaneous speech is fluent, many literal paraphasic errors, patient is AWARE of errors and tries to self-correct, auditory comprehension is normal, patient understands well but cannot repeat what is said

what is anomic aphasia

lesion locations variable —> maybe angular gyrus OR no clear localized lesions like in Alzheimers

syndromes where naming is most severe deficit —> fluent speech, some word finding pauses, otherwise normal looking neurological exam

intact: repetition, auditory comprehension, reading, writing

what are transcortical aphasias + list them

lesions on areas of the brain that project to the language cortex —> NOT affecting primary language cortex or circuit from Wernicke to Broca area

• lesions at various association cortex

3 types: Transcortical motor aphasia, Transcortical sensory aphasia, mixed transcortical aphasia

what is transcortical motor aphasia

Broca aphasia-like

lesions in left frontal lobe surrounding Broca area

• little speech, mute or short answers to questions, whisper

• preserved auditory comprehension, variable naming reading and writing

unlike broca: can repeat normally

what is Transcortical sensory aphasia

Wernicke-like

lesion in left posterio temporo-occipital lobe and with alzheimers

• speech is fluid but paraphasic, auditory comprehension is severely impaired, imparued reading and writing

unlike wernicke: patient can repeat phrases and sentences without difficulty

what is mixed transcortical aphasia

transcortical equivalent of global aphasia

• cannot speak fluently, cannot comprehend spoken langauge, cannot follow commands, impaired naming reading and writing

BUT patients CAN repeat frequently, even echolalic

What are subcortical aphasias + list them

aphasias defined by lesion localization rather than characteristics —> subcortical lesions disrupting connections to language cortex

list: anterior subcortical aphasia syndrome, thalamic aphasia

what is anterior subcortical aphasia syndrome

lesions at head of caudate nucleus, anterior limb of internal capsule, anterior putamen

characteristics: dysarthric speech, nonfluent speech, mild deficits of repetition and comprehension

what is thalamic aphasia

lesions of dominant thalamus

charactierized by: fluent aphasia with paraphasic errors, spared auditory comprehension, intact speech when patient is awake and praphasic speech when patient is drowsy

what is alexia

disordered reading

what happens in Alexia WITH Agraphia

lesion to LEFT inferior parietal lobule (+ supramarginal and angular gyri)

Acquired illiteracy: patient becomes unable to read OR write

spoken language intact; impaired auditory comprehension and naming to some degree

what happens in Alexia WITHOUT Agraphia

lesion from stroke near left posterior cerebral artery (supplies medial occipital and medial temporal lobes + splenium of corpus callossum

pure alexia = word blindness

• inability t o read

• normal spontaneous speech, repetition, auditory comprehension, some naming difficulty

• intact writing, but unable to re-read what is written

• also often have reduced short-term memory + right hemianopsia (vision)

  • lesion in left occipital = right hemianopsia

  • lesion of corpus callosum = no visual info transmitted from intact right occipital to the left hemisphre langauge centers (cannot decode written lanaguge)

what is aphasic alexia

reading disorder included in Broca aphasia —> more difficulty with reading comprehension than auditory comprehension

what is deep dyslexia

a defect in the basic reading process or in conversion of printed graphemes to spoken morephemes (a form of alexia)

• inability to read nonwords

• semantic and visual errors in reading words

• nouns and verbs are read better than closed-class categroies

due to large left hemisphere lesion (sign of significant mixed or Broca aphasia)

what is phonologic dyslexia

another type of alexia syndrome

• reading of single-content words = normal; and semantic errors = rare

• reading nonwords is difficult

• patients can read aloud by recognition of words meanings and by process of conversion of words to phonemes

• cannot convert individual letters to sounds

what is surface dyslexia

due to lesion in anterior left hemisphere + primary progressive aphasya

• patients can read phonetically by grapheme-to-morephem conversion but cannot recognize words directly

• rare

what is agraphia

pure agraphia = inability to write (minimal or no aphasic deficits

• not explainable by simple motor deficit, apraxia, or visuospatial difficulties

lesion in left siperior frontal region (mayeb left parietal lesions)

what are the two types of agraphia

phonological: production of the phoneme and then derivation of graphemes

• can write common words from dictation but cannot write dictated nonword phonemes

• similar to deep dyslexia

lexical: can write nonwords from dictation but cannot write irregularly spelled words + confused by homophones

what is apraxia

disorder of learned motor acts not caused by paralysis, incoordination, sensory deficit, or lack of understanding of desired movement —> inability to carry out skilled motor acts when commanded —> can do same movements when not asked

list the 3 types of apraxia

ideomotor, ideational, limb kinetic

what is ideomotor apraxia

failure to carry out motor act in response to verbal command when patient understands command and has motor capacity to perform same act under dif context

• command is decoded in Wernicke are —> disconnected from execution in premotor cortex of frontal lobe

  • part of the deficit in Wernicke aphasia

due to lesion in left hemisphere or lesions of corpus callosum preventing motor info from reaching right hemisphere motor area affecting left limbs

what is ideational apraxia (incl. the 2 competing definitions)

1st definition: pateint who could name objects BUT not demonstrate their uses —> lost the concept of the purpose

2nd definition: loss of ability to carry out multistep activity —→ each individual step performed appropruately

reflect motor planning difficulties —> frontal lobe lesions

what is limb-kinetic Apraxia

deficit of fine motor acts involving only one limb

mild pyramidal tract lesions —> difficulty with rapid or fine movement of fingers

sign of partial corticospinal tract lesion

what is agnosia

disorder of recognition —> usually affecting a single sensory system (though some can be more specific)

• has normal primary sensory perceptio, normal ability to name item once recognized, no dementia

  • eg. cannot recognize key ring by sight BUT able to identify and name it from sound of keys kingling or feeling keys in hand

most agnosias require bilateral cortical lesions —> cutting off input from sensory modality to left hemisphere language centers

what is agnosia in visual system

bilateral occipital lesions = cortical blindness

partial occipital lesions = permit perception of elements of object but unable to identify the item (eg. shown bicycle —> patient can report 2 circles and identify eyeglasses)

what is prosopagnosia

failure to identify faces —> subtype of visual agnosia —> cannot recognize family or friends but can describe features

• instead identify person by voice

what is auditory agnosia (list some)

bilateral lesions of temporal cortex —> disconnection from input from primary aidtory cortex to the Wernicke area

patients may have preserved pure tone hearing but cannot understand or repeat spoken langauge ==> pure word deafness

auditory nonverbal agnosia = preserved auditory recognition, identification of animal sounds or charateristic sounds associated with object s

phonagnosia = inability to recognize familiar voices

what is tactile agnosia

due to parietal lesions —> disrupts identification of objects by feel = asterognosis

• patient can describe sensory characteristic of object but cannot idenfiry it

agraphesthesia = inability to recognize letters or numbers drawn on hands

what is the definition of dementia

a gradual deterioration of previously intact cognitive functions —> often defined in terms of memory loss and at least one additional cognitive function (language, visuospatial functioning, apraxia, executive functionng)

what are the 3 classes of demential causes

1) systemic diseases (involving ogran systems outside CNS)

2)neurological diseases (degeneration of systems other than higher cortical functions)

3) diseases presenting mainly with loss of cognitive faculties

what are some systemic diseases that may causes dementia

• metabolic disorders (liver failure or kindkey failure) —> acute confusional state

• toxic disorders due to chemicals can cause Amnesia and true demensia if chronic use

• some infections like viral encephalitis and infectious meningitis, or AIDS

what are some neurological diseases associated with dementia

• hydrocephalus leading to atrophy

• basal ganglia diseases

• neurodegenerative diseases (Parkinsons/Lewy body dementia)

• Huntington disease

what is Alzheimers disease

a primary degenerative dementia that is defined by the presence of senile plaques in the neruopil of the cerebral cortex as well as neurofibrillary tangles in cerebral cortex neurons

what is a concussion

a head injury with or without brief loss of consciousness and brielf retrograde amnesia

• may have headaches, poor concentration and memory, insomnia, irritability, vertigo

what are contusions

bruising of the brain tissue or ppooling of blood in subdural or extradural space

• often occur directly under bony skull

• - impaired memory happens, impulsive behaviour, sometimes aphasias

what is white matter of the brain

axonal myelinated fibers for sharing information between and within hemispheric tracts

what are the three types of axonal tracts in the brain

1) projection

2) association

3) commissural

what are projection fibers

fibers that travel vertically to connect cortex with brainstem and spine —> usually carrying sensory and motor info

• prokect through the corona radiata and join a large fiber bundle in the internal capsule

what is the internal capsule

a structure located between the basal ganglia and the thalamus that containes fiber bundles of sensory and motor information as it travels from the thalmus to the cortices

• consist of 3 parts: (each assigned different types of fibers)

  • anterior limb

  • genu

  • posterior limb

what are association fibers

fibers connecting structures within the same hemisphere

• there rae short and long ones

list the short association fibres

arcuate fibers (they bend around a sulcus and connect two adjacent gyri)

what are the long association fiber bundles

• superior longitudinal fasciculus (aka arcuate fasciculus)

• cingulum

• inferior longitudinal fasciculus

• uncinate fasciculus

what is the superior longitudinal fasciculus

aka arcuate fasciculus

links frontal, parietal, occipital, temporal lobes

connect Wernicke area with Broca area