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left and right hemispheres have partily separate functions , leads to belive that two minds control our behaviour

producing and understanding language (verbal information )

controls movement on right side of body

controlling movement ( non verbal information )

music ,facial expression,visuospatial

controls movement on left side of the body

1. **lateralization is relative**
2. **cerebral site and side**
3. **environment affects laterality**
4. **range of animals also exibil lateralization**
5. **we act as if these is a single brain**

both hemispheres participate in nearly all behaviours (RH also has some language components)

are both as important frontal lobe asymmetrical but funtions are more similar to eachother than posterioir

more women have been found to be left handed than men

****not only related to the language component ( singing, mating etc seen in animals ) ****

not two different brains that work together but one

1. anatomical assymetry
2. asymmetry in neurological patients
3. asymmetry in the intact brain

1. RH is somewhat larger and heavier than LH : left part contains more gray matter than white matter (neurons)
2. difference in structure left and right temporal lobe :language/music
3. Sylvian fisure more steep on right than left
4. largel planum temporale (Wereinkle's area) left (language ) : 1 cm

1. gyrus van Heschl ( music) somewhat larger on the right : primary auditory cortex
2. distribution of neurons is asymmetrical in ot cortical and subcortical regions
3. RH sticks out a bit more in the front
4. LH sticks out a bit mmore in the back

compared dentric fiends of pyramidal cells in Broca's area :

dentric fiends of pyramidal cells in Broca's area left forntal opeculum (LOP)

facial area of motor cortex in left precentral cortex (LPC)

neurons in each region have distinct patterns of dentric branching

more branching allows cell more degrees of freedom in its function

there is abundant brencing in Broca's area (LOP)

ROP and RPC is not that arborised

1. unilateral lesions : double disasociation (Teuber)
2. split brain / disconnection
3. sodium amobarbital injection
4. brain stimulation

behavioural deficits as a result of stroke or surgery

LH lesions in right handed patients produce deficits in language functions ( speech, writing and reading ) : not produced by right hemisphere lesions

RH lesions produces deficits in performing spatial tasks, singing and playing musical instruments

! RIGHT HEMISPHERE LESIONS DISTURB TASKS NOT DISTURBED BY LEFT HEMISPHERE LESIONS

lesion in one brain area affects the function only designated to that area which goes in line with the lateralization theory

epileptic seizures may begin in restricted region of one hemisphere and sped through fibers of corpus collosum ( the comissure) to opposite hemisphere

in order to stop the spreading sometimes the nerves of corpus collostrum is cut

after sectioning, two brain regions are independent ( each control body musles and recieve sensory input ) : can no longer communicate with one another

functions can be studied without the other hemisphere

input from left side of the worlk goes to the right hemishphere (vice versa)

connection trough corpus callosum joins two sides

is corpus callosum severed, brain cannot join together the two viewa

when left hemisphere has acces to information → initiate speech ( talk about the expirince)

right hemisphere has reasonably good recognition but poor initiation of speech ( no connection to the left side)

abilities of the right hemisphere were demonstrated when the left hand, controlled by the right hemisphere picked up an object but still could not indentify the word correctly

when image is shown in the non speaking hemisphere (right) with the disconected speaking part, the person is unable to identify the object

1. anomic aphasia
2. object agnosia
3. acopia
4. apraxia

cannot have apraxia on right side ( ipsilateral apraxia = only on left )

right hemisphere cannot name visual information in left visual field

not able to recognise object with right hand ( with left is possible) with an intact visual system

able to see but not able to recognise it or its use

not able to draw/copy an object with the right hand

ca**rotid Sodium Amobarbital Injection**

language usaully located in left hemisphere

some people have alnguage in the right sime ( mostly left handed people )

by injecting sodium amobarbital in the carotid , a bried anesthesia is achieved

now uaully injected trough catheter insted of femoral artery

perosn cannot speak, move arm or see right visual field

right side is awake but most people do not have a dominant speach role here

**apraxia** : not being able to execute movementon command with an intact somatosensory motor system intact

injection in the right side porduces sesnosy and motor symptoms

no speech disturbance unless patient has right side dominance is speech

skull is opened

electrodes are placed on the brain tissue

apply electrical stimulation

provoke depolaristaion

we can see the action that arises (e.g. movement )

1. localized movements , dysesthesias, flases
2. interpretative or specific expirinces ( anxiety )
3. left frontal and temporal : increse in speexh
4. stimulation lbockks ongoing functions

1. asymmetry in visual system ( tachistoscopic examination )
2. asymmetry in the auditory system ( dichotic listening )
3. asymmetry in somatosensory system ( dichaptic test )
4. asymmetry in the motor system (crossed and uncrossed)

visual stimuli left field → right hemisphere visual stimuli right field → left hemisphere

less crossed than visual system but crossed connections. are stornger

preference left ear : melody

preference right ear : labguage

almost completrly crossed

right hand : complex movemnts (LH important in the analyisis of the order of movement )

left hand : visospatial task

1. it is indirect measure for the functioning of the brain lateralization test do not alweys match (e.g. sodium amobarbital)
2. lateralization test do not provide reliable information about individual differences in neuronal pathways to the cortex
3. attitude of the patient alweys important for the test results
4. repeated lateralization tests within the same person do not alweys yield same results

1. language and speech ( reading and writing )
2. temporal ordering ( language motor activity )
3. fine anlyisis ( identify faces )
4. visual system ( letters and words)
5. auditory : language realted sound

1. attention and arousal ( subcortical connections )
2. processing of complex visual information ( face, gestalt )
3. language : complehansion of words, semantic memory , understand context, emotion of language
4. speech prosody
5. auditory : music

1. many functions are nor asymmetrical ( primary sensory and motor areas)
2. functional differences between both hemispheres are relative
3. cerebral site vs side
4. left hemisphere is not the 'language hemisphere' but considerably involved in the process, right hemisphere is concerned with visuospatial functions