Pierre Krolak-Salmon

The human brain is expert in analyzing rapidly and precisely facial features, especially emotional expressions representing a powerful communication vector. The involvement of insula in disgust recognition has been reported in behavioral and functional imaging studies. However, we do not know whether specific insular fields are involved in disgust processing nor what the processing time course is. Using depth electrodes implanted during presurgical evaluation of patients with drug‐refractory temporal lobe epilepsy, we recorded intracerebral event‐related potentials to human facial emotional expressions, that is, fear, disgust, happiness, surprise, and neutral expression. We studied evoked responses in 13 patients with insular contacts to specify the insular fields involved in disgust processing and assess the timing of their activation. We showed that specific potentials to disgust beginning 300 milliseconds after stimulus onset and lasting 200 milliseconds were evoked in the ventral anterior insula in four patients. The occurrence and latency of event‐related potentials to disgust in the ventral anterior insula were affected by selective attention. The analysis of spatial and temporal characteristics of insular responses to disgust facial expression lead us to underline the crucial role of ventral anterior insula in the categorization of facial emotional expressions, particularly the disgust. Ann Neurol 2003

The first electrophysiological study of the human lateral geniculate nucleus (LGN), optic radiation, striate, and extrastriate visual areas is presented in the context of presurgical evaluation of three epileptic patients (Patients 1, 2, and 3). Visual‐evoked potentials to pattern reversal and face presentation were recorded with depth intracranial electrodes implanted stereotactically. For Patient 1, electrode anatomical registration, structural magnetic resonance imaging, and electrophysiological responses confirmed the location of two contacts in the geniculate body and one in the optic radiation. The first responses peaked approximately 40 milliseconds in the LGN in Patient 1 and 60 milliseconds in the V1/V2 complex in Patients 2 and 3. Moreover, steady state visual‐evoked potentials evoked by the unperceived but commonly experienced video‐screen flicker were recorded in the LGN, optic radiation, and V1/V2 visual areas. This study provides topographic and temporal propagation characteristics of steady state visual‐evoked potentials along human visual pathways. We discuss the possible relationship between the oscillating signal recorded in subcortical and cortical areas and the electroencephalogram abnormalities observed in patients suffering from photosensitive epilepsy, particularly video‐game epilepsy. The consequences of high temporal frequency visual stimuli delivered by ubiquitous video screens on epilepsy, headaches, and eyestrain must be considered.

Diagnosis of inflammatory optic neuropathy is very likely in a young adult presenting acute, unilateral and painful visual loss. Relative afferent pupillary defect is a very sensitive and specific sign of optic neuropathy. Ophthalmological exam is mandatory to estimate severity of visual loss, appearance of optic disks and check for another eye disease. Magnetic resonance imaging is indicated to rule out a compressive optic neuropathy and to quantify the inflammatory lesion index, which is the best prognostic indicator of multiple sclerosis development (MRI is abnormal at entry in about 50% of patients with isolated optic neuritis). Spontaneous outcome of optic neuropathies is favourable. Corticosteroids have demonstrated efficacy only in shortening length of evolution and by using parenteral high doses. Clinical benefit from introducing beta-interferons treatment after a first episode of isolated optic neuritis remains to be evaluated. Secondary inflammatory optic neuritis (infection, vasculitis, sarcoïdosis) are rare and usually present atypical evolution or other symptoms.

Event‐related potentials (ERPs) were recorded in 10 adult volunteers, who were asked to view pictures of faces with different emotional expressions, i.e. fear, happiness, disgust, surprise and neutral expression [Ekman, P. & Friesen, W.V. (1975). Pictures of Facial Affect. Consulting Psychologist Press, Palo Alto, CA]. ERPs were recorded during two different tasks with the same stimuli. Firstly, subjects were instructed to pay attention to the gender of the faces by counting males or females. Secondly, they had to focus on facial expressions by counting faces who looked surprised. The classical scalp ‘face‐related potentials’, i.e. a vertex‐positive potential and a bilateral temporal negativity, were recorded 150 ms after the stimulus onset. Significant differences were found, firstly between late‐latency ERPs to emotional faces and to neutral faces, between 250 and 550 ms of latency and, secondly, among the ERPs to the different facial expressions between 550 and 750 ms of latency. These differences appeared only during the expression discrimination task, not during the gender discrimination task. Topographic maps of these differences showed a specific right temporal activity related to each emotional expression, some particularities being observed for each expression. This study provides new data concerning the spatio‐temporal features of facial expression processing, particularly a late‐latency activity related to specific attention to facial expressions.

Bilateral paramedian thalamic infarcts are characterised initially by the association of acute vigilance disorders and vertical gaze palsy, followed by persisting dementia with severe mnemic disturbance, global aspontaneity and apathy. We describe a patient with a dramatic neuropsychological recovery, confirmed by testing examination and completed by a cerebral metabolism study. The pathophysiology of this type of cognitive deficit is discussed.

AIMS To determine the course of optic nerve radiations in the temporal lobe, especially their retinotopic organisation and the anterior limit of the Meyer's loop. METHODS 18 adult patients who had undergone a tailored temporal lobectomy for epilepsy were included in this study between 1994 and 1998. The rostrocaudal extent of the lateral temporal lobe resection assessed intraoperatively by the surgeon and by postoperative MRI was compared with the postoperative visual fields determined by automated static perimetry (ASP). RESULTS 15 patients (83%) presented a postoperative visual field deficit (VFD) confined to the superior homonymous field contralateral to the side of the resection. All degrees from a minimal upper field loss to a complete quadrantanopia were observed. The VFDs were somewhat stereotyped, predominating along the vertical meridian. The smallest anteroposterior resection resulting in a VFD was limited to 20 mm from the tip of the temporal lobe. A relation was observed between the extent of the lateral resection in front of the second and third convolutions and the occurrence and extent of postoperative VFDs. No patient reported persisting subjective visual impairment. CONCLUSION The high frequency of postoperative VFDs appears to be due to the greater sensitivity of ASP. The characteristics of the stereotyped VFDs allow new conclusions about the course and retinotopy of optic nerve radiations. The anterior limit of Meyer's loop is likely to be located more rostrally than previously believed.