Lesion studies lesion studies part of

Lesion studies

lesion studies • part of “reverse engineering” • classical neyropsychology: specific brain regions (can try to associate brain region to function) • cognitive neuropsychology: infer building blocks of cognition irrespective of where they are located in the brain • what (neural components) vs where • lesion: disruption to a component in a cognitive model • lesion: a region of organic brain damage • group studies vs. single case studies • establish lesion-deficit associations (classical) • how cognitive processes might be subdivided (cognitive) • neurosurgery (e. g. epilepsy, lobotomy), tumors, strokes, anoxia, traumatic head injuries, viral infections, neurodegenerative disorders, TMS

dissociations & associations • single dissociation: impaired on a particular task A but relatively spared on another task B • task-resource artifact: A requires more of the cognitive/neural resource • task-demand artifact: performs task A suboptimally (e. g. misunderstood instructions) • double dissociation: 2 patients/brain-areas + 2 tasks • for cognitive neuropsychology these (cognitive systems) need not even lie in different brain locations • association of deficits? weak evidence for functional relation between them (e. g. nearby brain location) • syndromes: clusters or associations of different symptoms/deficits

group studies • classical neuropsychology (but single-case also) • lesions are typically large and rarely restricted to the region of interest • considering several patients helps localising which region(s) is critical for a given function • (a) grouping by syndrome (e. g. schizophrenia, aphasia) • (b) grouping by cognitive symptom (e. g. auditory hallucinations, difficulty in reading non-words) • (c) grouping by anatomical lesion: classical approach, lesions can be extensive but there is a single part which is common • method (b) is relatively new(er) and can potentially reveal more than one region as being critically involved • test predictions from (c) with f. MRI and vice versa • try everything!

animal models • • electric current, suction device (irreversible) neurochemicals, cooling down (reversible) more specific location but not perfect compare pre- and post- lesion performance • • • but. . need not be the only function of that area need not be the only area for that function lesioned area might be the early part of a processing chain diaschisis: disrupt the functioning of distant brain regions that are structurally intact (via white matter damage) • plasticity? • non-specific factors • control task (each animal serves as its own control) • control group (surgery no lesion, lesion elsewhere)