Juvenile play in the rat: thalamic and brain stem involvement.

Discrete electrolytic lesions of the parafascicular area of the thalamus (PFA) or posterior thalamic area (TP) reduced the frequency of pinning, an indicator variable for rough-and-tumble play in juvenile rats, while largely sparing motivation to play. Similar sized lesions placed within the ventrobasal thalamic area (VBT) had minimal effects on both pinning and measures of play solicitation. Lesions placed within the ventrolateral aspect of the brain stem also markedly reduced pinning, while having no effect on indices of play motivation. Although tests designed to assess the extent to which the observed play deficits may be attributable to a loss of somatic acuity proved inconclusive, the overall pattern of results were not inconsistent with positing a role for these neural areas in relaying somatic stimuli relating to playful intent.