Language, brain asymmetry, and consciousness Flashcards
Language and the aphasias
Aphasia - an impairment in language production/understanding that is caused by a brain injury. Lesions in the left anterior frontal Broca’s area interfere with speech production. Damage to the tempoparietal Wernicke’s area interferes with language comprehension. Pathway between these two for synchronization of production and comprehension. Aphasias are impairment in language - stroke, aneurysms, etc. Damage to Broca’s area causes nonfluent aphasia - difficulty with speech production but not language comprehension. Hemiplegia involving one side of the body is common in nonfluent aphasia.
Agnosia and aphasia
Damage to left posterior speech zone (Wernicke’s area) causes fluent aphasia. They produce plenty of verbal output, but it is full of paraphasias, such as sound or word substitutions. People are losing meanings of words. Global aphasia is damage to both. Conduction aphasia - lose white matter tracts that communicate between the two.
Where words make sense
Language processing involves many regions in both hemispheres. Will get a reductionistic perspective if you only look at certain sections of the brain. Different parts of language stored in different parts of the brain, just like memory. Brain is an integrated network. These findings are inconsistent with human lesion studies suggesting that semantic representation is lateralized to the left hemisphere.
Disintegration
Severing of corpus callosum: In most people, vocabulary and grammar are the exclusive domain of the left hemisphere. Participants were then asked to touch several objects they could not see and select the correct one. Such a task could be performed correctly by right and not left? Visual input can cross the optic chiasm but not the linguistic stuff.
Wada test
Done before brain surgery to see where language is. Whichever side is anesthetized and produces the language deficit.
Consciousness
The state of awareness of one’s own existence, thoughts, emotions and experiences. Neuroscience has made good progress in understanding pattern identification, visual reconstruction, but far from explaining the complexities of human subjective experience. There is likely no central consciousness area of the brain - no central self node.
Consciousness as integrated information
Two primary components - 1 every observable conscious state contains massive amount of information. Ex: single frame of movie. 2 in the conscious mind, information is highly and innately integrated. Impossible for you to see world apart from all the info you are conscious of. Ex: when seeing an orange, you can’t separate the color from the shape. Consciousness is integrated: even though color processing and spatial processing are separately localized in the brain, conscious experience cannot be atomized into distinct parts - ex stroke and split brain. Phi coefficient is mathematical index of degree of conscious integration of information. Higher when awake than when asleep. (combo of TMS and EEG). If person not awake, activation more local. Consciousness is moving away from brain being separate nodes of activation to a system operating in collaboration. Awake: probe activation extends elsewhere, asleep: not much spreading. Vegetative patients who show cortical integration are likely conscious.
Consciousness, free will, and neuroscience
Free will is the feeling that our conscious self is the author of our actions and decisions. Conscious mind is a pattern generator - often generates patterns for things that are not pattern-based: emotion, creating meaning out of activation patterns. Does neuroscience challenge that? The conscious mind generates meaning or patterns from preconscious processes. Although we may think we make decisions consciously and deliberately, research “may” suggest otherwise. We all post-hoc make a meaning or interpretation of us deciding to do something. Even applies to deliberate decisions - can see 10 secs before person makes a decision to press a button. Challenges free will/illusion that we are in control of everything, a lot of decisions happen below conscious awareness.
