37 terms

Hemispheric Assymetry

Gina Grimshaws lectures and readings on hemispheric assymetry
Are we right or left-brained?
Neither - coordinated efforts of both hemispheres is needed
How do we investigate the brain?
Brain damaged patients (unilateral, split-brain), neuroimaging, perceptual assymetries
first to tie function with anatomy, leading to assumption that left was the most important and intelligent side of the brain
Contralateral organisation
Damage to the left side of the brain leads to problems with the right side of the body
language disturbances
Reading problems
Motor problems
Associative Agnosia
Difficulty recognising objects
Left hemisphere damage leads to
Aphasia, Dyslexia, Apraxia, Associative Agnosia, Depression
Broca, 1860
Localised language to left frontal lobes
What is a stroke?
heart attack in the brain - blocked blood vessels - causing holes in the brain
Jackson, 1878
Localised spatial awareness to the right hemisphere - also that it had a role in language
Right hemisphere damage leads to
Aprosodia, loss of meaning, Amusia, loss of spatial awareness, Hemispatial neglect, prosopagnosia, euphoria, anosognosia
No emotional tone in voice
Loss of music
Hemispatial neglect
Attentional problems
Difficulty recognising faces
Lack of awareness of deficits
How do the hemispheres work together?
Speech perception, vision, emotion
Speech perception
LH - words and syntax, RH - expression, tone, meaning
LH - details, RH - big picture
LH - positive emotions (approach), RH - negative emotions (avoid)
Electrical Stimulations - when, on what
Penfield 1930s, during surgery to map language areas
Wada test - what
Inject sodium amytal (amobarbital) into middle cerebral artery on left or right side
What joins the two side of the brain?
Corpus callosum, 2 million axons connect L and R cortex
How do patients have split brains? - why
Callosum cut (to control epileptic seizures), but subcortically still intact
How do split brain patients behave?
Normal, but competition between hands
What is learnt from split-brain patients?
LH - speech production, RH - language abilities (reading of concrete words, auditory, skips to meanings), visual-spatial abilities
Perceptual Assymetries
LVF projects to RH and viceversa, Left ear projects to RH and vice versa
Structural imaging - 2, meaning
CT, MRI, Can reveal structures but not involvement in behaviours
Functional imaging
computerised tomography, X-rays taken at different angles to construct brain picture
Magnetic Resonance Imaging, passing magnetic field through brain and detecting reverberations
Functional Magnetic Resistance Imaging, detect changing aspects of brain physiology without radiation, gives 3D image or brain at work showing active parts
Electroencephalography, detects electrical currents from neurons, by affixing electrods to the head, indiates activity at brain's surface
Positron emission tomography, 3D localisation of brain function, injecting with radioactive sugar absorbed by brain cells according to level or activity
Transccranial magnetic stimulation, series of magnetic pulses at a location causing disturbances directly underneath it, temporary lesion