Brain Damage and Mental Function

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Where are the lesions associated with alexia and agraphia?: angular and supramarginal gyri (in parietal lobe)
aphasia: difficulties in the expressive use of speech
agnosia: - disorders of recognition and perception
- a loss of ability to recognize objects, persons, sounds, shapes or smells while the specific sense is not defective nor is there any significant memory loss
- It is usually associated with damage to the temporal lobe
- fail Mooney's face test and Unconventional views test
anosagnosia: - the tendency to ignore or sometimes deny the fact that one has a problem/is paralyzed
- most often seen with right hemisphere damage
- patient may confabulate when asked to move paralyzed arm
right and left hemisphere associations: right - associated with reality

left - associated with schematics and planning
Cases that indicate that certain areas of the brain are specialized: - the woman whose right arm tried to strangle herself

- spontaneous smile vs. forced smile
Where does a natural/spontaneous smile originate from?: basal ganglia (limbic system)
natural gait vs. marching: natural gait originates in basal ganglia

marching involves the motor cortex
too little dopamine vs. too much dopamine: - Parkinson's disease
- too little dopamine = shuffling gait, parkinson's disease
- too much dopamine = chorea (excessive involuntary movements), schizophrenia
Most striking evidence of specialization: lesion studies/evidence
prosopagnosia: - impairment in facial recognition
- damage in temporal lobe (usually right hemisphere)
Capgras Syndrome: - patient thinks parents/loved ones are impostors
- disconnection between limbic system (amygdala) and visual system
Cotard's Syndrome: Patient believes s/he is dead
arcuate fasciculus: - connects the posterior part of the temporoparietal junction with the frontal cortex in the brain.
- in left hemisphere
- connects Broca's area to Wernicke's area.
- Damage can cause conduction aphasia
conduction aphasia: - damage to arcuate fasciculus (connects Broca's and Wernicke's areas)
- speech output sounds like Wernicke's patient
- syntactically normal but semantically abnormal
- comprehension intact
- difficulty in repeating words
- cannot read, alexic
Alexia: - inability to read or name letters of the alphabet
- lesion in left visual cortex
Agraphia: - inability to write
- lesion in left angular gyrus
How come an alexic can still recognize numbers and objects?: -numbers: don't know. Maybe strong tactile connection with numbers and fingers
-objects: are polymodal, have many different attributes that they can be recognized by
somatosensory map - Penfield homunculus: - located on postcentral gyrus of parietal lobe
- entire body is upside down, but head is right side up
- from top of head, down to side: genitals, foot, trunk, hand, thumb, face, lips, pharynx
- cortical magnificaiton: face and hand take up more space than other parts of the body
body image: a brain's internal image and memory of one's body in space and time
Medulla Oblongata: -connects spinal cord to the brain
-controls critical functions like bp, hr, respiration
-connects to pons
Pons: connects medulla to cerebellum
Cerebellum: - concerned with coordination of movements and timing
- coordinates muscular activity
- acheives motor control by receiving information from all around the body
cerebral cortex: - outer part of each hemisphere
- where thinking and planning take place
- activation of entire cerebral cortex leads to arousal and wakefulness
- activation of a small portion leads to selective attention
thalamus: - all sensory information except smell passes through it before reaching the outer cortical mantle
- evolutionarily more primitive
- main control center of sensation and movement
- all pathways travel to and from it
- damage can cause tremor, involuntary jerky movements, dystonia (uncontrolled movements), Parkinson's disease
hypothalamus: - regulates metabolic functions, hormone production, and various basic drives such as aggression, dear, and sexuality
- influences eating, drinking, sleeping and waking, sexual behavior, organization for flight or fight and rage reactions, and response to reward and punishment
hippocampus: - controls laying down of new memories
- in temporal lobe
Lateral Fissure: - Sylvian Fissure
- separates frontal and temporal lobes
Central Fissure: - Rolandic
- separates frontal and parietal lobes
relative localization: - most functions can be assigned to a region of the cortex but without precise localization to specific cells
- the higher the function, the higher the degree of integration and the less localized the system
Neuroma: - popular explaination for phantom limbs
- frayed and curled up nerve-endings at the site of the amputation become inflamed and irritates, fooling the brain into thinking the missing limb is still there
cell's receptive field: each cell on the somatosensory cortex has its territoryy on the body surface to which it corresponds
dorsal rhizotomy: procedure in which all the nerve fibers carrying information from one arm into the spinal cord are completely severed
one explaination for phantom limb pain: as the brain adjusts to the loss of a limb and cells slowly make new connections, there is a slight error in the remapping so that some of the sensory input from touch receptors is accidently connected to the pain areas of the brain
Patient was born without arms but she has phantoms that can move. What does this suggest?: - the neural circuitry for her body image must have been laid down at least partly by genes
- body image is not strictly dependent on motor and tactile experience
What creates and maintains your body image in the brain?: - parietal lobes combine information from sources such as muscles, joints, eyes, and motor command centers
primary motor cortex: concerned mainly with simple movements (like wiggling fingers)
supplementary motor cortex: - associated with more complex motor skills (like waving goodbye)
- passes specific instructions about the proper sequence of required movements to the motor cortex
When commands are sent from the supplementary motor cortex to the primary motor cortex, where else does the informationg go?: - identical copies of the command signal are sent to the cerebellum and parietal lobes, informing them of the intended action.
What are the cerebellum and parietal lobes important for?: - help to compare your intention with your actual performance and modify the motor commands as needed
- parietal lobe contains your body image
What 2 sources does the phantom limb experience arise from?: - remapping (via sprouting and activation of latent connections)
- each time time motor command center sends signals to the missing arm, info about the commands is also send to the parietal lobe containing our body image
- the convergence of info from these two sources results in a dynamic image of the phantom limb that is continuously being updated
Parietal Lobes: - responsible for sensory convergence of vision, hearing and touch (also muscle and joint sense)
- creates an internal representation of the external world, including own body
- concerned with discerning the spatial layout of the external world
- allow you to navigate through space, reach out for objects and know where you are
hemianesthesia: - primary sensory loss on one side of body
- damage to parietal lobe
hemineglect: - damage to right parietal lobe
- complete indifference and neglect of left side of world
- left side of memories are neglected also
- if patient's attention is drawn to left side, will notice left side
parietal lobe damage can cause: - inability to determine tactile quality
- loss of joint sense
- disordered spacial orientation (can't see mooney faces)
When you glance at any visual scene, what happens to what you see?: - the message from the eyes is mapped onto the primary visual cortex. From there it is relayed onto the "how" and "what" pathways
What is the "how" pathway?: -info from the primary visual cortex is sent to the parietal lobes
- parietal lobes are concerned with discerning the spatial layout of the external world, allow you to navigate through space, reach out for objects and know where you are
What is the "what" pathway?: - info from the primary visual cortex is sent to the temporal lobes
- temporal lobes are concerned with recognizing and naming individual objects and responding to it with the appropriate emotions
Temporal Lobes: temporal lobes are concerned with recognizing and naming individual objects and responding to it with the appropriate emotions
reticular activating system: - tangle of neurons starting in the brain stem (reticular formation) that projects widely to vast regions of the brain
- All areas of the brain are interconnected in a + feedback loop that takes a stimulus from the outside world, extracts its salient features and the bounces it from region to region before eventually figuring out what it is and how to respond to it
- is believed to be the center of arousal and motivation
Frontal Lobes: - concerned with abstract processes such as judgement, foresight, and planning
Limbic System: - concerned with emotional behavior
- evaluation of the emotional significance and potential value of events in the external world
Why does neglect only occur with right parietal damage?: - the right hemisphere of the brain is specialized for emotions and holistic/global aspects of sensory processing. It has a broad "search light" that covers both the right and left side of the world
- the left hemisphere is specialized for language, and has a narrower search light that only covers the right side of the world.
- therefore, if left side gets damaged, the right side's search light can still notice things in both sides of the world, but not vice versa
mirror agnosia: - when prompted to reach for an object that a patient sees in a mirror, the patient reaches into the mirror instead of in the area that the object actually is in space
Explanations for mirror agnosia: - the left side of the patient's world just doesn't exist so to them, the object must be inside the mirror
- difficulty with spatial task is because of parietal damage, not neccessarily due to the neglect itself. Patient can't do the proper mental gymnastics
Visual Agnosia: - associated with lesions of the left occipital lobe and temporal lobes
Why do normal people engage in psychological defense mechanisms?: the left hemisphere takes in all the info given to it and organizes it into a stable belief system. But, if some new information comes along that doesn't fit into your belief system, you can't just rebuild your whole belief system, so you then resort to Freudian defenses: denial, repression, confabulation, and self-delusions
- allows coherence and stability within your own mind
- left hemisphere will do anything to maintain the status quo
Why are defense mechanisms so exaggerated in agnosognosia patients?: - right hemisphere questions the status quo and looks for global inconsistencies. when anomalous info reaches a threshold, it forces a complete revision of the entire model/belief system
- doesn't matter what side the discrepancy comes from, the right hemisphere is always activated
- so if right side is damaged, the left hemisphere is free to pursue it's denial and confabulation as far as it wants
reaction formation: - a subconscious attempt to disguise something that is threatening to your self-esteem.
- may explain anosognosia
astereognosis: - loss of the ability to recognize objects by touch
- patient is unable by touch alone to name objects, describe them or demonstrate their use or significance
asymbolia / pain asymbolia: - unable to recognize the nature of an object from the somatosensory information alone
- pain asymbolia - failure to correctly interpret pain sensations from areas of the body and are usually indifferent to pain
allesthesia: - attention is paid to the spatial elements on the previously neglected side, but they are treated as if they were on the unaffected side
- associated with parietal damage
simultaneous extinction: - the patient responds normally and attends effectively to both sides of space until there is simultaneous competing stimulation of both side. In that case, neglect of the side opposite of brain damage will occur.
- associated with parietal damage
apraxia: - loss of intentional movements
- associated with parietal damage
cerebral commissurotomy: - cutting the corpus callosum so that the two hemisphere can no longer exchange information
- patient referred to as split brain patient
- initially inteded to stop epileptic seizures from spreading from one hemisphere to the other
effects of commissurotomy: - general lack of handicap
- since vision is contralateral, if something is shown in the left visual field, it is registered in the right occipital lobe: patient will know what is it but will not be able to verbally identify it since language is specialized on the left side, and the information cannot be transferred to the left hemisphere
- if object is placed in left visual field (seen by right hemi), can be picked up by left hand (controlled by right hemi), but not by right hand
synesthesia: - A condition in which one type of stimulation evokes the sensation of another, as when the hearing of a sound produces the visualization of a color.
- associated with medial inferior of temporal lobe
- may be a crosswiring in color area and number area: in fusiform gyrus or angular gyrus
lower synesthete: - cross-wiring in the fusiform gyrus
- V4 color area is near number area
- the color is driven by the visual appearance of the number, not numerical concept: roman numerals are not associated with color
higher synesthete: - cross-wiring is in angular gyrus
- the color is driven by concept of sequence: any kind of sequence of numbers, days of the week, months of the year, have an associated color
subitising: rapid, accurate, and confident judgments of number performed for small numbers of items just by looking at it
semantics vs. syntax: meaning vs. grammar
Broca's aphasia: - severely impaired speech output
- speech reduced to nouns and verbs
- meaning and word order intact
- difficulty with repetation and naming
- language comprehension intact. Can read
Wernicke's aphasia: - characterized by a severe deficit in auditory comprehension
- related impairment in reading and writing
- difficulty with repetation and naming
- unintelligible, gibberish speech output
Wernicke's area: - superior middle and posterior regions of the temporal lobe
- larger in left hemisphere than in right hemisphere
anomic aphasia: - angular gyrus or supramarginal gyrus is damaged
- difficulty in finding words
- low vocabulary
- no comprehension of metaphors
- otherwise comprehension intact
- semantics and syntax intact
- damage to left A.G. - left/right condusion, dyscalculia
- cannot repeat
anomia: - difficulty in finding the right words or the inability to remember names
- can repeat words
transcortical aphasias: damage to the border zone surrounding classical language areas
Stages of normal memory: - perception
- contextual encoding
- short term memory buffer
- long term memory
- retrieval (recognition + free recall)
retrograde amnesia: - failure to remember things that took place prior to what caused the amnesia
- things in the recent past are more likely to be lost and the older memories are more resistant to being lost
antirograde amnesia: - a form of amnesia where new events are not transferred to long-term memory, so the sufferer will not be able to remember anything that occurs after the onset of this type of amnesia for more than a few moments.
- damage to the hippocampus, fornix, or mammillary bodies
Korsakoff's syndrome: - antirograde amnesia caused by alcoholism (thiamine deficiency)
- can be caused by hypoxia (low blood pressure) or infections also
- intact short term memory
- confabulation (similar to right parietal damage)
- lack of awareness of passage of time
- anosognosia
- can acquire procedural and declarative memory, but won't remember actually acquiring it
- intact IQ
- mild euphoria
Parts of the Limbic System: - Insular cortex
- Amygdala
- Septum: associated with pleasure
- Hypothalamic Nuclei
- Mammilary Bodies
- Fimbria and Fornix
- Nucleus Acumbens: associated with pleasure
- (Hippocampus)
- Anterior Cingulate
- Frontal Lobes
What part of the brain does the Rabies virus infect?: Libmic System
Input to the Limbic System: - vision, touch, hearing, taste, smell
- sense of smell has dominant input because smell information goes straight from olfactory bulbs to limbic system
What applies brakes to limbic activity?: anterior cingulate
Output from Limbic System: - Affective (subjective emotions)
- Behavioral (the four F's)
- Autonomic: sympathetic or parasympathetic
- Hormonal
Kluver-Bucy Syndrome: - lesion in limbic system
- visual agnosia
- indiscriminate sexuality
- indiscriminate oral explorations
Hypothalamic Lesions: - satiety center (nucleus): rats will keep eating
- appetite center: won't eat food but will drink water
- sexual nuclei
- pleasure center: give a high feeling
- septum: stimulation creates an orgasmic feeling
Temporal lobe epilepsy: - characterized by complex sensory, motor, and psychic symptoms such as impaired consciousness with amnesia, emotional outbursts, automatic behavior, and abnormal acts
Temporal lobe personality - interictal: - personality changes, temporal lobe personality
- hypergraphia
- argumentative, stickyness in conversastion, egocentric, obsessive, hyper religiosity
Damage to frontal lobes: - loss of higher attributes that define us as humans:
- morals, abition, empathy, etc.
- general change in personality
reticular activating cortex: - in brain stem
- responsible for working memory
- allows you to hold information long enough to plan something
- attention
Frontal Lobe Syndrome: - grasp reflex (undamaged FL's inhibit grasp reflex)
- loss of impulse control
impairment of:
- judgement
- perseveration
- morality
- planning
- ambition
- personality
- social norms
- sense of responsibility
motion blindness: bilateral damage to middle temporal (MT) area
color blindness: bilateral damage to area called V4 (in fusiform gyrus)
In visual system, what is the old and new?: - Old path: from eyes to superior colliculus (to parietal and higher cortical areas)
- New path: from eyes, to lateral geniculate nucleus to primary visual cortex to where/how and what pathway to
"Where/how" pathway in visual system: - from lateral geniculate nucleus to "where" pathway in parietal lobes
- associated with motion and position in space, visually guided motions
"What" pathway in visual system: - from lateral geniculate nucleus to "what" pathway in temporal lobes
- associated with object identification, object's emotional significance, and color information
Blindsight: - damage to primary visual cortex
- can't "see" but can still reach out and grab something in that area
- "new" pathway damaged, but "old," orienting pathway is still intact
Broca's area: inferior posterior frontal cortex of left hemisphere
Transcortical motor aphasia: - lesions in frontal association cortex (anterior and superior to broca's area)
- doesn't understand speech
- cannot read
- can repeat without impairment
Transcortical sensory aphasia: - lesion in peri-sylvian association cortex (junction of parietal and temporal lobes)
- language reception is severly affected but ability to repeat is intact
Septum: - cluster of cells near the front of the thalamus in the middle of the brain (limbic system)
- activation of this areas creates intense pleasure
inner emotional life vs. outward expression of emotions: inner: connections between amygdala and frontal lobes
outward: hypothalamus

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