Summary:To study the effects of focal infarction on the capacity for functional activation of an ipsilateral somato sensory system remote from the lesion, we produced a small thrombotic infarct in the left frontal pole of male Wi star rats by a photochemical method. Five days later, the awake, restrained rats received tactile stimulation of the large whiskers (vibrissae) of the right side of the face, while a double-label 14C-autoradiographic study of local CMRglc (lCMRgJc) and local CBF (lCBF) was performed. Unlesioned and unstimulated animals served as controls. In rats without frontal infarct, vibrissae stimulation led to activation of ICMRglc in the three synaptic relay stations of the barrel-field pathway (ipsilateral trigeminal medul lary nucleus, contralateral ventrobasal thalamus, and contralateral barrel-field cortex). The mean increment in ICMRglc was 42% in lamina IV of barrel-field cortex and 49% in ventrobasal thalamus. Normalized ICBF tended to increase in superficial cortical laminae. In unstimulated animals with frontal infarct, ICMRglc was reduced by 20-30% throughout the ipsilateral barrel-field cortex asThe concept of diaschisis-an acute or subacute suppression of neural function in intact brain re gions remote from a site of primary injury-has at tracted increasing attention as one of several factors possibly relevant to functional recovery after isch emic stroke (Feeney and Baron, 1986). Although the application of modern techniques for assessing regional brain function has contributed importantly