1. Frontal lobe

2. Occipital lobe

1. Sylvian fissure

2. horizontal

3. upward

1. Planum temporal

2. left

Area of the brain at the end of the Sylvian fissure that is 10x larger in the left hemisphere than the right.

The left Planum Temporale is known as the language center of the brain.

Area in the left hemisphere that is critically important for speech output

Has more dendritic branching in left hemisphere than right, indicating higher specialized processing capacity

Neurochemical differences in the brain:

Larger concentrations of ______ are found in the right ________ than the left, while there are larger concentrations of, and more receptors for, _______ in the left _______ than the right.

1. norepinephrine

2. thalamus

3. dopamine

4. globus pallidas

Those who had their right temporal lobe removed as an epileptic procedure displayed prosopagnosia and other agnosias of hard-to-name objects

**First published proof that cerebral dominance was not true

Demonstrated by Roger Sperry in 1974, looked at hemispheric differences of patients w/severed corpus callosum (commissurectomy)

1. Distinct speech localization in the left hemisphere: When patients were asked to feel a hiden object with one hand, they could verbally name the object if it was presented in the right hand, but not if it was presented in the left hand.  On the other hand, if the patient was asked to demonstrate the use of the object, they performed very well if the object was in the left hand

2. Distinct spatial, nonverbal localization in the right hemisphere: When asked to draw 3-D objects or shown chimeric figures and asked to identify, the right hemisphere performed better than the left

**Important to note that these patients were not necessarily representative of population--low sample size, all had epilepsy, some with low IQ

Injected a barbituate into each carotid in time, made note of deficits on each side of brain

1. Left hemisphere lesions disrupt language function

2. Right hemisphere lesions disrupt spatial (ie--understanding world cues/mapping of location) and visuospatial (ability to differentiate things you experience--see, hear, etc.) function; ie-unable to differentiate line locations, pitches of sound, tone of voice, emotional expression of faces, identify objects in their incorrect orientation

Research with Neurologically Intact People:

Visual Methods

1. Divided visual field procedure: take advantage of wiring of visual system

2. Bilateral presentation: Object is presented in each side of the visual field

3. Unilateral presentation: Present only one object, entirely in one field

Presentation to one visual field or the other results in superior responding (an observable difference in speed and accuracy from one side of the brain)

**Rapid presentation of material is required because eye movements can affect which side of the brain the information is going to

Research on Neurologically Intact People:

Tactile and Auditory Methods

Dichaptic presentation: Person asked to feel two items simultaneously, one in each hand, then to identify these items in some way or another

Dichotic presentation: Different information presented simultaneously to each ear so that each hemisphere receives two competing pieces of information--information from the ipsilateral ear is suppressed relative to information from contralateral ear

Tactile: Right hand better at recognizing a letter drawn in the palm, sandpaper letter identification, but if feeling two complex shapes and asked to match them to visual stimuli, left hand is better

Auditory: Speech sounds better in right ear, non-speech sounds better in left ear

Engaging in a task causes greater activity in the hemisphere dominant in that task, and the greater activity results in an attentional increase to the contralateral field, further enhancing processing of the same type of information

**If a stimulus activates part of the brain, it is easier to stay active

1. Difference in processing basic sensory features

2. The hemispheres differe not in what they process but in how they process information

Spatial frequency: Low frequency is useful for general form (right hemisphere) and high frequency is better for detail (left hemisphere

*Important: All RELATIVE frequency; high relative frequencies recognized better in right regardless of absolute frequency

Characterization of Hemispheric Differences:

Differences in Mode of Processing

Left hemisphere is piecemeal and analytical with emphasis on temporal relationships

Right hemisphere is holistic, Gestalt with emphasis on spatial relationships

*Both sides contribute to the performance of a task, rather than one side "napping" while other does the work

1. Right

2. Gestalt

3. Left

4. Analytical

**Seeing the "big picture" is a right hemisphere task, while focusing on details is a left hemisphere task

Made up of 3 parts: Jenu, Body, and Splenium

Front part connects to front parts of the brain, back part to back parts of the brain--different parts of corpus callosum relay different information

Body carries motor information

Splenium carries visual information

**NOTE: Many other commissures connect hemispheres subcortically

General, "dichotomous" comparisons (male-female, young-old)

Emotional tone, ie.-recognizing familiar faces as good or bad

**Brain specailization occurs developmentally early

Evidence:

*Planum temporale is developmentally different at birth (without experience)

*Gyral pattern present before birth

*Magnitude of perceptual asymmetry DOES NOT increase with age (left language preference doesn't increase with age in children)

While 95% of right handed people have language center on left, spatial on right, only 70% of left handed people have language on left and spatial on right; 15% have language on right, 15% have language on both

*Similar case with planum temporale

*Parts are larger in non-right handed men than right handed men, but not true for women (sex hormone?)

*Splenium more bulbous in women

Women: When progesterone and estrogen are high, there is more left lateralization (fine motor skills are improved) and less right (poor mental rotation of objects); effect reversed w/low levels

Men: Intermediate levels of testosterone associated with better spatial performance

+1.  Improved ability to extract different but compatible information simultaneously

+2. Lateralization allowed for the best expression of manual and vocal skills

+3. Motor performance is best if the sensory feedack goes to the same hemisphere

-4. Motor functions would be better if only one hemisphere was involved to avoid cross-hemisphere conflict

-5. Language comprehension and production work best if both are in the same hemisphere (avoid callosal degradation

+6. Temporal precision required in language would be impaired if both hemispheres were involved

+7. Both motor skill (handedness) and language require efficient sequencing so are co-lateralized

The number of muscle fibers innervated by a single motor neuron

Less for more precise movements, more for larger movements

Motor Tracts:

Corticospinal Path

From the cortex to the spinal cord

Start at the precentral gyrus (primary motor cortex)

--Lateral: Crosses in medulla and controls independent movement of distal muscles

--Somas located in the motor cortex

--Damage affects ability to reach, grasp, and manipulate objects

--Ventral: Trunk and upper legs; important control for running, walking, and posture; ipsilateral and contralateral connections

Motor Tracts:

Cortibulbar Path

From the primary motor cortex to the face (via pons, location of the cranial nerves)

--Somas in the cortex, synapse on cranial nerves

--Control of upper face is both ipsilateral and contralateral, but lower face is all contralateral

Motor Tracts:

Ventromedial Paths

(Tectospinal, vestibulospinal, and reticulospinal)

Origin in subcortical areas (tectum, vestibular system, and reticular activating system, respectfully), indirect link to motor cortex

--Responsible for posture, eye movement, head/neck movement, sneezing, breathing, muscle tone, walking

Motor Tracts:

Dorsolateral-Rubrospinal Path

Origin in red nucleus

Controls movement of distal muscles independent of trunk

Cerebellum:

General Properties

Two hemispheres with three areas:

vermis, intermediate, and lateral

--Forms loops with other motor areas: checks and balances of whether actual movement match the planned movement

--Ipsilateral connections

--Center areas control posture and speech

--Lateral areas control limbs and eyes

Inner core of cerebellum

--Site of somatosensory and kinesthetic input from spinal cord

--Output through the fastigial nucleus

--Controls ventromedial paths

--Damage leads to postural and walking problems

--Input from red nucleus and somatosensory information from spinal cord

--Output through interpositus nucleus to red nucleus

--Damage leads to rigidity and difficulty in moving the limbs--"action tremors"

--Input from motor and association cortex through the pons

--Output through the dentate nucleus and ventrolateral thalamus

--Damage affects ballistic movements (overshooting movements), coordination of multi-joint movements, and learning new movements

--Input usually through the caudate, nigrostriatal bundle and putamen and output through the globus pallidus or neostriatum

*Globus pallidus gets input from the neostriatum and the subthalamic nucleus

--Output can influence eye movement through the superior colliculi

--Loops in the prefrontal cortex and cerebellum for monitoring and modifying motor responses

*Slow developing motor movements

*Posture

*Preparation for voluntary acts

*Autopilot for well-learned behaviors

*Timing and switching between motor acts

*Motor planning and learning, especially with motivated behaviors (reward) or cognitive components (unlearning one response and learning an new one)

**Direct connections activate to sustain activity, indirect paths activate to suppress activity

Caused by insufficienct dopamine in parts of putamen, due to cell death in substantia nigra--less activity in the direct paths, so indirect paths are overactive and suppress movement

--Symptoms include akinesia (lack of spontaneous movement, facial spontaneity, speech difficulties), bradykinesia (slowness of movement), posture disturbances, cogwheel rigidity (muscles don't relax, force movement) and resting tremors

***Caused by genetic degeneration, striatal damage (caudate and putamen), loss of striatal GABA neurons from striatum to globus pallidus; damage indirect paths from striatum to internal globus pallidus, less inhibition of movement

***Symptoms include hyperkinesia such are chorea (uncontrollable jerky movements), athetosis (writhing contractions and twisting body into unusual positions), cognitive deficits, and psychiatric symptoms

Signs show problems with correcting and stopping movements

--Compared to the precise orientation specificity of the columns of cells in the visual cortex, coding for the direction of movement is more a population vector sum

--Cells seem to code for direction, degree of muscle force and torque, trajectory and distance to target

--Damage to the motor cortex results in less force and imprecise fine movements

--Also require motor plan from areas that project to motor cortex for timing and sequencing of movements (ie-motor program)

Motor Plan:

--The _____ codes for the abstract plan

--The ______ codes for more specific details

--The ______ codes for actual muscle movment

1. Supplementary motor area

2. Premotor area

3. Primary motor cortex

--Plans, prepares, and initiates movement

--Evidence: Firing in the SMA precedes firing in the limb

--Both sides control for behavior on either side, especially in complex behaviors

--Activated wen just imagining that the act is being performed

--Contains subregion that is activated when performing task at the same time as someone else

--Contains "mirror cells": fire when activity is being performed in front of you that you know how to do

--Provides neural basis for understanding and duplicating the actions of others, including communication

--Posterior section implicated in movements that are novel or require cognitive control; neurons in this area fire even in anticipation of activity

--Tested with the Stroop colors test

--There are differences within areas of the ACG

Conjugate lateral eye movements--right side controls leftward movements, left side controls rightward movements

--Control voluntary movements of the eyes while superior colliculi control reflexive reactions to stimuli

--Eye fields suppress reflexive movement

Two functions:

1. Interface between movement and sensory information (superior); where everything comes together

2. Contributes to the ability to produce complex, well-learned motor acts (inferior)

Links motor plan to body position

--Proprioceptive (touch) and kinesthetic (movement) feedback coupled with information from motor planning areas allows the adjustment of ongoing movement

--Damage causes misguided movements (no motor feedback)

--Controls complex, well-learned behaviors

--Area links visuospatial and internal representation information together with the motor plan (even in imagination)

--Damage may cause apraxia

--Damage to left results in impaired pantomime and gesturing (no objects present)

--Damage results in loss of the ability to mentaly model a movement

Two Models for Sensory-Motor Plans:

The ____ Model: Knowing what a certain movement should produce so that monitoring and correction can take place

The ____ Model: The desired sensory states are determined, then the motor program to achieve those states is selected; plan continuously changes

1. The forward model

2. The inverse model

Increase dopamine levels with L-dopa

Decrease cholinergic activity (restore balance and reduce tremors)

Experimental therapies:

Fetal tissue transplants, destruction of internal segment of globus pallidus, stimulation of subthalamic nuclei

Rigid, bradykinesic form: More rapid decline and intellectual impairment (tremor form)

Akinesia associated with depleted dopamine and homovanillic acid (HVA) in caudate: tremors

Symptoms include vocal and motor tics, repetitive involuntary and compulsive behaviors

*Level 1: Facial tics, may be touching and jumping

*Level 2: Cries and vocalizations

*Level 3: Echolalia, coprolalia (obscene speech)

Genetic, runs more in females, associated with OCD

Drugs that block dopamine receptors help (bad side effects including depression, weight gain, lethargy); increasing dopamine makes symptoms worse

--Levels of HVA (dopamine metabolizer) lower in children with disorder; probably due to hypersensitivity of DA receptors

Symptoms include increased movements, usually of mouth and lips, could include chorea, tics, compulsive hyperactive fidgety movements of the legs (akathisia) and continual painful muscle spasms (dystonia)

Caused by hypersensitivity to DA receptors in basal ganglia caused when depletion of DA in substantia nigra occurs

Anticholinergic drugs and DA blockers help, but only in about 1/2 of patients

--Possible to get overlapping of symptoms with Parkinson's symptoms (possibly due to D1 vs. D2 receptors)

Limb moves on its own, doesn't belong to the person or has its own "personality"

--Usually affected contralateral to a stroke

--Possibly caused by blockage in cerebral artery

Inability for perform skilled movements, not the result of simpler damage (ie--not from another disorder); motor plan affected; usually in the left hemisphere

Can perform movements spontaneously but not when asked to--higher order damage

Ideomotor Apraxia

ALL definitions

Disconnection between idea and the execution of movement--understand the concept but cannot perform the act

OR

can't imitate gestures that do not act on an object

OR

problem in the timing and speed of a motion--cannot coordinate

Ideational (Conceptual) Apraxia

ALL definitions

Inability to imagine a movement in sequence (but can perform each step in isolation)--cannot make a motor script

OR

Inability to use actual object

OR

Inability to connect an object with the correct motions

Affects left limb only

No response to verbal requests

*Not true apraxia