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 fMRI 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)