Experiment 1 – Bias type实验1–偏置式.docVIP

Running Head: REORGANIZATION AND RECOVERY A Model of Cortical Reorganization and Recovery from Brain Damage Jacques A. Katz Carnegie Mellon University and the Center for the Neural Basis of Cognition Advisor: Jay McClelland Committee: Dave Plaut Richard Koerber Abstract Many researchers have noticed the apparent age dependence of the effects of brain damage. Such dependence has traditionally been attributed to biological effects of age, such as neural pruning. A connectionist model is presented in which the age dependent effects of brain damage emerge from an experience driven competition between brain areas. This competition develops based on two general factors: the commitment of resources in a task dependent way, and a bias favoring short connections. The results suggest that recovery is linked to the reorganization of proximal cortical areas, and depends highly on experience both before and after brain damage. “I am convinced that a lesion… apt to produce lasting aphasia in an adult, will not prevent a small child from learning to talk” (Broca, as quoted by Finger Almli, 1988, p. 122). The effects of brain damage are striking and nowhere near fully understood. One trend appears to be clear however. Across a large number of different types of brain damage, brain damage incurred at early ages tends to be less severe than similar lesions in adulthood (Kennard, 1938; Kolb 1987, 1999; Kolb et al., 1987, 1996). Likewise, brain damage incurred at other times in development seems to have a more severe effect (see Hebb, 1947, 1949; Wilson, 1998). The recovery of lost behavioral or cognitive function after brain damage at any age appears to depend on the ability of the cortex to reorganize. Functions require some cortical substrate to support their performance. Only through the reorganization of the cortex remaining after damage can lost function be recovered. Fortunately, human cortex appears predisposed to this ability to reorganize, often referred to as