posterior association cortex
TRANSCRIPT
Association cortices
Motor Sensory Association
Somato Sensory Pathway
Sensory Cortex Receptive Field
Two Point Discrimination
Columnar organization of somatosensory cortex
Sensory Cortex
somaticProprioceptive
Area 5 integrates tactile information from mechanoreceptors in the skin with proprioceptive inputs from the underlying muscles and joints. This region also integrates information from the two hands. Area 7 receives visual as well as tactile and proprioceptive inputs, allowing integration of stereognostic and visual information. The posterior parietal cortex projects to the motor areas of the frontal lobe and plays an important role in sensory initiation and guidance of movement.
Association Cortex Information Flow
Pattern of Vibration of the Basilar Membrane
The Auditory Cortex
Discrimination of Sound “Patterns” by the Auditory Cortex
Pathways to the somatosensory, visual, and auditory association areas
Visual Pathway
AIT = anterior inferior temporal area; CIT = central inferior temporal area; LIP = lateral intraparietal area; Magno = magnocellular layers of the lateral geniculate nucleus; MST = medial superior temporal area; MT = middle temporal area; Parvo = parvocellular layers of the lateral geniculate nucleus; PIT = posterior inferior temporal area; VIP = ventral intraparietal area.) (Based on Merigan and Maunsell 1993.)
Pathways to the somatosensory, visual, and auditory association areas
Unimodal sensory inputs converge on multimodal association areas
Interaction Among Association Areas Leads to Comprehension, Cognition, and Consciousness
Emotion Localization
Parietal Lobe
Left Hemisphere
Cortical Sensory Loss
Disorder of language
Fluent aphasia, alexia
Gerstman’s syndrome (Angular gyrus)
acalculia,
finger agnosia,
left/right disorientation,
agraphia
Tactile agnosia (bimanual asteriognosis)
Bilateral Ideomotor & ideational apraxia
Right hemisphere
Cortical Sensory Loss
Topographic disorientation
Topographic memory loss
Anosognosia /dressing apraxia
Constructional apraxia
Hemi-inattention
Apraxia of eye opening
Confusion
“Attention Neurons” in the Monkey Parietal Cortex
Attention activity of Right Parietal Cortex in Normal
Contralateral Neglenct Syndrome
Temporal Lobe
Either Temporal dysfunction
Auditory– Threshold of brief auditory stimuli elevated – Spoken words less clear– Distorted words are less clear– Difficulty in equalizing sound presented to both ear– Rapidly presented words and number in both ear difficult to
perceiving
Hallucination– Auditory,– visual, – olfactory and
– gustatory Emotional and behavioral changesDelirium
Left temporal dysfunction
Auditory deficits (right ear) – Intracranial localization of sound is impaired. – Increased threshold for perception of short bursts of sound. – Increased threshold for some frequencies. – Failure to perceive brief simultaneous auditory stimulation.
Visual deficit (both eyes)
– Upper right quadrantanopsia. Other complex sensory deficits
– Right hand tactile performance difficulty. – Right hand finger agnosia.
Left temporal dysfunction
Language deficits – Decoding of speech sounds (phonemes) is impaired.
– Problems with verbal repetition.
– Problems with auditory comprehension of speech.
– Receptive aphasia (deficits in all language qualities).
– Impairment of dichotic listening to verbal material.
– Intellectual impairment on verbally mediated intellectual processes.
Memory impaired for verbal material.
Emotional disturbances – Perceptual distortions, alterations of mood, obsessional
thinking, psychosis, temper outbursts, hypo and hypersexuality
Right Temporal dysfunction
Right temporal lesion effects tend to be notable statistically but of less
clinical significance.
1.Visual analysis (nonverbal primarily) – Impairment of simple and complex
visual analysis, but some negative findings.
– Impairment of short-term nonverbal memory.
– Impaired perception of tachistoscopically-presented letters.
– Prosopoagnosia (especially with anterior lesions).
– Impaired recognition of objects seen from unusual angles
3. Auditory analysis (nonverbal)
– Impairment of short-term auditory
memory.
– Perception of short sounds
impaired.
– Impaired recognition of familiar
sounds.
– Impaired tonal discriminations,
timbre discriminations, and
amplitude discriminations.
– Amusia.
– Impairment of contralateral ear
input in dichotic listening.
Right Temporal dysfunction
4. Constructional tasks – Visual construction impairment
proportional to tissue loss.
– Impairment in maze learning (visual and proprioceptive feedback).
– Enlarged left-hand margin in dictation.
5. Psychiatric personality phenomena with right temporal epilepsy – Personality changes.
– Psychiatric symptoms.
– Deja vue.
– Metamorphopasias.
6. Psychometric findings
– Temporary decline in Performance IQ following lobectomy.
– Impairment on WAIS Picture Arrangement.
– Impairment on Binet Memory for Designs
– Possible impairment of WAIS Block Design?.
7. Persistence in maintaining a hypothesis even after being informed it was not correct.
Bitemporal dysfunction
Human bitemporal lesion– Kluver bucy like + aphasia, amnesia and bulimia
Bilateral inferior and medial temporal lesion– Sham rage like
– React to every stimuli with extreme belligerence, screaming, cursing , biting and spiting
Bilateral post cortical lesion
– Cortical deafness – unaware of deafness
Korsakoff amnesic defect
Selective activation of face cells in the inferior temporal cortex of a rhesus monkey
Prosopognosia
Occipital Lobe
Unilateral occipital lesion
Contralateral (congruent) homonymous hemianopia, may be
central (spitting the macula or peripheral
Homonymous hemiachromatopsia
Elementry unformed hallucination – irritative lesions
Left occipital lesion
Right homonymous hemianopia
Alexia and color naming defect with deep white matter or
splenium of corpus callosum involved
Visual object agnosia
Right occipital lesion
Left homonymous hemianopia
Visual illusion, (metamorphopsias), and hallucinations
Loss of topographic memory and visual orientation
Bilateral occipital lesions
Cortical blindness
Anton syndrome
Loss of perception of color
Prosopognosia and simultagnosia
Balint syndrome
Balint Syndrome (Bilateral parietooccipital region)
An inability to look voluntarily into the peripheral field, with normal
eye movements (psychic paralysis of fixation gaze)
A failure to precisely grasp or touch an object under visual
guidance, hand and eyes in- coordinated (optic ataxia)
Visual inattention affecting mainly the periphery of the visual field,
attention to other sensory stimuli being intact
Failure to properly direct occulomotor function in the exploration of
space (amorphosynthesis)
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