Two patients with bilateral thalamo-mesencephalic infarct in the paramedian territory developed vertical gaze dysfunction and marked behavioural changes, in the absence of significant motor inability and formal neuropsychological impairment. While they were physically and emotionally active before stroke, they became apathetic, aspontaneous, indifferent, and seemed to have lost motor and affectic drive, as well as the need itself for any psychic activity. However, this mental and motor inertia was reversible when the patients were repeatedly stimulated by another person. This need for constant external programming, together with a lack of emotional reactivity, made the patients resemble robots. CT and MRI suggested involvement of the dorsomedial and midline nuclei of the thalamus, and SPECT showed remote frontomesial hypoperfusion. A disturbance of the striatal-ventral pallidal-thalamic-frontomesial limbic loop is suggested by previous reports of a similar "loss of psychic self-activation", "pure psychic akinesia", or "athymhormia" with bipallidal, bistriatal, or subcortical bifrontal lesions.