He had no other epilepsy risk factors, with normal developmental milestones before the onset of his epilepsy. Direct electrical stimulation of that area elicited topographic visual hallucinations.Ī 22-year-old left-handed male was referred for surgical evaluation for medically refractory epilepsy, which appeared after West Nile viral encephalitis at the age of 10. A place-selective area in the posterior collateral sulcus and medial fusiform gyrus was identified using functional MRI (fMRI) and iEEG. Here, we report the results of a multimodal investigation into the function of place-selective cortex in the basal temporal lobe in a patient implanted with intracranial electrodes as part of the surgical approach to drug-resistant focal epilepsy. In one cortical stimulation study where visual areas were identified by fMRI, stimulation of the PPA did not elicit any complex visual hallucination ( Murphey et al., 2009). However, topographic hallucinations have not been reported upon stimulation of scene-selective visual cortex. Penfield's pioneering work demonstrated complex visual perceptions elicited by electrical stimulation of the temporal and frontal lobes ( Penfield and Perot, 1963 Blanke et al., 2000). These results suggest that the PPA is necessary for the representation of local visual scenes ( Epstein, 2008).Īpart from the aforementioned lesion studies, there is little causal evidence linking neural activity in the PPA to the visual perception of scenes. Patients who sustain lesions involving this area have trouble navigating both familiar and unfamiliar environments ( Epstein et al., 2001). The PPA responds to visual scenes, whether familiar or not, in a viewpoint-specific manner ( Epstein, 2008), and with low response latencies, as evidenced by recent intracranial EEG (iEEG) work ( Bastin et al., 2013a, b). More recently, functional neuroimaging has disclosed a network of cortical areas that selectively activate when viewing scenes or buildings, including the parahippocampal place area (PPA Aguirre et al., 1998 Epstein and Kanwisher, 1998). During the last century, several observations of patients with topographic disorientation have implicated brain areas at the junction of the basal temporal and occipital lobes, predominantly in the right hemisphere, in this ability ( Landis et al., 1986). Our results support the causal role of the PPA in the perception of visual scenes, demonstrate that electrical stimulation of higher order visual areas can induce complex hallucinations, and also reaffirm direct electrical brain stimulation as a tool to assess the function of the human cerebral cortex.Ī sense of place is paramount to our ability to recognize and navigate the world around us. By contrast, stimulating the more lateral aspect of the basal temporal lobe caused distortion of the patient's perception of faces, as recently reported ( Parvizi et al., 2012). Bipolar direct electrical stimulation of a cortical area in the collateral sulcus and medial fusiform gyrus, which was place-selective according to both fMRI and iEEG, induced a topographic visual hallucination: the patient described seeing indoor and outdoor scenes that included views of the neighborhood he lives in. Here, we combined functional magnetic resonance imaging (fMRI) and intracranial EEG (iEEG) recordings to delineate place-selective cortex in a patient implanted with stereo-EEG electrodes for presurgical evaluation of drug-resistant epilepsy. Beyond the observation that lesions involving the PPA cause topographic disorientation, there is little causal evidence linking neural activity in that area to the perception of places. In recent years, functional neuroimaging has disclosed a network of cortical areas in the basal temporal lobe that selectively respond to visual scenes, including the parahippocampal place area (PPA).
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