The insula; further observations on its function.

read a paper to the American Neurological Association in Atlantic City in which he described results of stimulating the cerebral cortex in 163 awake adults undergoing intracranial surgery. Later that year he published , with Edwin Boldrey (1906–88), 'Somatic motor and sensory representation in the cerebral cortex of man as studied by electrical stimulation' (Brain 1937: 60; 389–443). Section 28 deals with 'The quality of cortical sensation': 369 responses elicited a sensation, the quality of which was not stated; 204 responses were described as tingling or electric; 131 stimuli induced numbness ; 49 responses involved a sense of movement; and 'eleven times the patient reported a sense of pain in one extremity or peripheral part; it was never severe. .. and never caused the patient to object'. Seventeen years later, and working with a different co-author, ME Faulk Jr, former research fellow at the National Institutes of Health, Penfield returns to his studies on the insula— the hidden cortex on the island of (Johann Christian) Reil (1759–1813)—regarded by early anatomists and physiologists as a centre for speech or taste. Unlike the experimental animal which 'cannot speak and must be anaesthetised'. .. 'a patient usually shows a keen, and often impersonal, interest in the activity of his own cerebral cortex'. But their recordings, made during procedures planned with no purpose in mind except the cure and comfort of the patient, have to be opportunistic: 'all too often when the golden opportunity presents itself, we lack the wit to ask the right question!'. Because Penfield has previously observed abdominal sensations and gastrointestinal mobility following stimulation of the insula, and others have developed the concept of a vagomotor centre regulating autonomic activities in the insular-orbital region— orchestrating a feeding pattern formed as a downward extension of motor representation in the cortex that engages mastication, salivation, swallowing, oesophageal contraction, and inhibition of respiration and contractions of the pyloric antrum—Dr Faulk has developed a technique for gastromotor recording (including gastric electric potentials sampled by a swallowed silver–silver chloride electrode in contact with the gastric mucosa), together with monitoring of respiration and intra-arterial blood pressure, during local anaesthesia in man. Now Penfield and Faulk report on all 36 patients treated surgically for focal epilepsy in whom stimulation of the insula was performed at the Montreal Neurological Institute (Canada) between 1945 and 1953, including those previously reported. They use a square wave generator producing current at a …