Paradoxical functional facilitation in brain-behaviour research A critical review

The aim in this review article is to document research findings that have shown paradoxical effects of nervous system changes, whereby direct or indirect neural damage may result in facilitation of behavioural functions. Such findings have often been ignored or undervalued in the brainbehaviour research literature. A further aim is to consider possible mechanisms and theoretical insights related to this facilitation. Analyses of relevant studies show that two major types of paradoxical functional facilitation (PFF) effects may be distinguished, (i) Situations where damage to intact brain tissue brings to normal or near normal a previously subnormal or abnormal level of functioning. I refer to improved levels of functioning in such contexts as restorative PFF effects. One of the best documented examples of such PFF effects is the 'Sprague effect', whereby collicular lesions may bring about an improvement in visual functioning following an initial occipital lesion, (ii) Situations where a subject with nervous system pathology or sensory loss performs better than normal control subjects on a particular task. I refer to improved levels of performance in these contexts as enhancing PFF effects. Restorative and enhancing PFF effects have