1 / 51
Cerebral Lateralization
Click the card to flip 👆
Terms in this set (51)
Hippocampal Commissurelarge bundle of axons that connects the right and left hippocampal formationsMyers and Sperry cut corpus callosum in cats-Patch one eye -Each hemisphere can learn independently -Learned tasks as well as in controlled conditions -No memory or savings was demonstrated when patch was transferred to the other eye -With intact cats, learning is transferred between the hemispheresSperry and Gazzaniga cut corpus callosum in peoplehemispheres in split brains of humans are not equal: -When present a picture to the right visual field (left brain --cannot tell what it was --right hand can show, but left hand can't -When present a picture to the left visual field (right brain) --Will report that they do not know what it is --Left hand can show, but right hand can'tCommissurotomytransect the corpus callosum to reduce the severity of convulsionsDual foci of attentionsplit brains can search for target item faster than intact brainsHelping Hand Phenomenonwith two different visual stimuli - the hand that "knows" may correct the otherChemeric Figures Taskonly the right half of the face is recognizedVisual Competitionfilling in, or completion of scotoma by the brain.Z LensLimits visual input to one hemisphere of split brain patients while they scan complex visual materials Also used to compare speech abilities between right and left hemispheresSplit-Brained PatientsMost are left-hemisphere dominant. In those that aren't, there can be conflict between the hemispheres. Difficult tasks are likely to enlist the involvement of both hemispheresSplit-Brained PeterBoth hemispheres often disagreed Emotional information somehow passed between hemispheresLeft HemisphereInterpreter superior, in control of ipsilateral movement plays a greater role for memory in verbal materialRight Hemispheresuperior in spacial ability, emotion, music ability, artistic ability and some memory tasksInterpreterhypothetical neuronal mechanism that continuously assesses patterns of events and tries to make sense of themFrontal OperculumBroca's Area -Near face area of primal motor cortex -language production -Right has larger area, left has larger volumePlanum TemporaleWernicke's Area -Temporal lobe, posterial lateral fissure -Language comprehension -Left larger in 65% of peoplePrimary Auditory CortexHeschi's gyrus -Two gyri on right, one on leftTheories on Evolution of Cerebral LateralizationAnalytic-synthetic: left brain = analyzer, right brain = synthesizer. Difficult to test Motor: left brain specializes in control of movement, does not suggest why motor function became lateralized Linguistic: Primary role of left brain is language. W.L could still pantomime, though he could no longer sign due to his brain damage of left hemisphere Evidence exists that lateralization began before humans -neurons are more efficient when completing specific tasks if concentrated in one hemisphere -we can do more at the same time, if the two tasks occur in separate hemispheresVocal Communication in Nonhuman Primatessubstantially different between vocal production and auditory comprehension attributed to inability to control vocal chordsMotor Theory of Speech PerceptionPerception and comprehension of speech depends on the words activating the same neural circuits in the motor system that would that would be activated if the listener said the wordsGestural LanguagePrimates are advanced with hand gesturesBroca's AreaSpeech production -Damage leads to expressive aphasia -Speech is meaningful, but halted and awkwardWerkicke's Areaspeech comprehension -Damage causes receptive aphasia -Speech sounds normal but it "word salad"Conduction AphasiaArcuate fasciulus that connects Broca's and Wernicke's -inability to repeat words just heard -comprehension and speech are normalAlexia and AgraphiaLeft angular gyrus: posterior to Wernicke's area Damage causes Alexia and AgraphiaWernicke-Geschwind ModelLanguage is localized in the left-hemisphere and goes through a pathway starting in the primary visual cortex then goes forward into the gyrus, AF, Brocas, Wernickes areas and then back to the Primary Auditory Cortex Surgery that destroys all of Broca's area, but little of the surrounding tissue, has no lasting effects on speech. -lesions also do not have a huge effect -Wernicke's area being removed also did not see lasting effects.Major Findings from Brain ImagingNo aphasic patients have damage restricted to Broca's or Wernicke's area. They usually have damage to the subcortical white matter Anterior lesions - expressive symptoms Posterior lesions - receptive symptoms Aphasic patients may not have damage to Wernicke-Gerschwind areaGlobal Aphasiamassive lesions on anterior and posterior cortex and in white matterlanguage as mosaicdiscrete columns of tissue that perform a certain function widely distributed throughout the language area of the cortexReading SentencesfMRI scans showed areas of activity were tiny and spead out. Areas of activity varied between subjects and trials Activity was widespreadPET Study of NamingImages were shown of famous faces, animals and tools -Left temporal lobe activated by naming varied per category -Activity was seen well beyond Wernicke's areaCurrent Premise of LanguageMediated by activity in all areas of the brain that participate in the cognitive process involved in the particular language-related behavior Speech, comprehension, and reading is accomplished by the combination of several constituent cognitive processes which may be organized separately in different areas Cognitive neuroscientists typically divide analysis into 3 categories: phonological, grammatical, and semantic. Areas of the brain for language are not dedicated solely to language language areas are likely to be small, widely distributed and specializedDyslexiareading difficulties not due to some other deficit (vision, or intelligence)Acquired Dyslexiadue to brain damage - relatively rareDevelopmental Dyslexia50% heritability more common in boys some brain differences subtle visual problems can be seenReading Out LoudLexical: use stored information about words Phonetic: sound out words from the lettersSurface Dyslexialexical procedures lost- can't recognize words Left parietal and temporal lesions Errors like "quill" for "quail"Deep DyslexiaCan't sound out unfamiliar words Extensive damage to left hemisphere Errors like "hen" for chickenNeglectInability to pay attention to contralesional side after parietal or frontal lesions, and can affect vision, audition, and tactionExtinctionINability to pay attention to a contralesional object when there is a ipsilesional object which seems to be caused by lesions to the temporo-parietal juntionSimultanagnosiainability to pay attention to more than one object a time, typically caused by bilateral parietal lobe damage