Recovery of function after brain damage: The chronic consequence of large neocortical injuries.

Abstract

In the present experiment we addressed the common clinical finding that subsequent to recovery of function, there is often a lingering chronic dysfunction associated with extensive neocortical injury. We have confirmed this observation in the laboratory setting, and the data is compatible with the theoretical position that brain injury induces a shift in dominance of functional neural systems that normally control behavior. Although the present data do not suggest how this shift in dominance may be reversed, it does, nonetheless, demonstrate that the persistent chronic dysfunctions associated with neocortical injury may be effectively moderated within certain environmental situations.

Recovery of function after brain damage: The effects of nimodipine on the chronic behavioral deficit

“…Severely limiting the conditions under which a behavior may be expressed is one strategy to reduce the chronic long-term consequences of brain injury (Chappell & LeVere, 1988). Unfortunately, although these controls may produce a statistically significant improvement in behavior and be of some conceptual importance, they reveal little about the cause of the long-term deficit and are so restrictive that they are clinically irrelevant.…”

“…For example, if lesioned animals are tested for long periods of time subsequent to reaching criterion performance after brain injury, it is quite apparent that the recovery is often incomplete. In fact, their performance is usually some 5 to 15 percentage points lower than that of normal subjects tested on the same problem (Chappell & LeVere, 1988;Cooper, Freeman, & Pinel, 1967;Lashley, 1930;LeVere & Mills, 1977). And the data indicate that this deficit is chronic and long-term and does not change or subside, even when testing continues for many months after brain injury.…”

“…Notwithstanding the tenacious character of this longterm deficit, the deficit can nonetheless be manipulated by controlling certain conditions of the test situation. Reducing the time between individual test trials, for example, will significantly lower the number of errors committed by a visual decorticate rat tested on a learned brightness-discrimination task, whereas increasing the time between test trials will significantly increase the number of errors (Chappell & LeVere, 1988). Normal animals are, however, quite unaffected by either of these manipulations.…”