Complementary deficits in perceptual classification in pure alexia and acquired prosopagnosia - New insights from two classic cases.

Pure alexia and prosopagnosia traditionally have been seen as prime examples of dissociated, category-specific agnosias affecting reading and face recognition, respectively. More recent accounts have moved towards domain-independent explanations that postulate potential cross-links between different types of visual agnosia. According to one proposal, abnormal crowding, i.

Impaired visual search with paradoxically increased facilitation by emotional features after unilateral pulvinar damage.

Posterior thalamic pulvinar nuclei have been implicated in different aspects of spatial attention, but their exact role in humans remain unclear. Most neuropsychological studies of attention deficits after pulvinar lesion have concerned single patients or small samples. Here we examined a group of 13 patients with focal damage to posterior thalamus on a visual search task with faces, allowing us to test several hypotheses concerning pulvinar function in controlling attention to visually salient or emotionally significant stimuli.

Review: Tales from Both Sides of the Brain.

Our brain has two hemispheres that specialize in different jobs-the right side processes spatial and temporal information, and the left side controls speech and language. How these two sides come together to create one mind is explained by pioneering neuroscientist Michael Gazzaniga in his new book, Tales from Both Sides of the Brain : A Life in Neuroscience (Ecco/Harper Collins, 2015). Gazzaniga is director of the SAGE Center for the Study of the Mind at the University of California, Santa Barbara, and a Dana Alliance member.

Detection of Right-to-Left Cardiac Shunt in the Absence of Transcranial Acoustic Bone.

Purpose: Paradoxical thrombotic embolism via right-to-left cardiac shunt (RLS) is a risk factor of cryptogenic ischemic stroke. Transtemporal Doppler (TTD) is a valid method used in the detection of patent foramen ovale (PFO). Temporal acoustic bone windows are missing with increasing age and in some younger subjects.

Submillisecond unmasked subliminal visual stimuli evoke electrical brain responses.

Subliminal perception is strongly associated to the processing of meaningful or emotional information and has mostly been studied using visual masking. In this study, we used high density 256-channel EEG coupled with an liquid crystal display (LCD) tachistoscope to characterize the spatio-temporal dynamics of the brain response to visual checkerboard stimuli (Experiment 1) or blank stimuli (Experiment 2) presented without a mask for 1 ms (visible), 500 µs (partially visible), and 250 µs (subliminal) by applying time-wise, assumption-free nonparametric randomization statistics on the strength and on the topography of high-density scalp-recorded electric field. Stimulus visibility was assessed in a third separate behavioral experiment.

Neurological and robot-controlled induction of an apparition.

Tales of ghosts, wraiths, and other apparitions have been reported in virtually all cultures. The strange sensation that somebody is nearby when no one is actually present and cannot be seen (feeling of a presence, FoP) is a fascinating feat of the human mind, and this apparition is often covered in the literature of divinity, occultism, and fiction. Although it is described by neurological and psychiatric patients and healthy individuals in different situations, it is not yet understood how the phenomenon is triggered by the brain.

"Crossed" somatoparaphrenia: an unusual new case and a review of the literature.

Somatoparaphrenia is a delusional misidentification and confabulation of body parts, usually arm or hand, opposite to a cerebral lesion, generally of the "minor" right hemisphere. There is some controversy concerning lesion site (fronto-parietal; parieto-temporal; posterior insula, additional subcortical nuclei) or necessary associated symptoms (hemiparesis/plegia, anosognosia, neglect, position sense deficit). We here present a patient who is unusual in many respects, that is: (1) he is a right-hander with somatoparaphrenia after a "dominant" left-hemisphere lesion associated with aphasia and ideo-motor apraxia, but also with right hemineglect.

Very early processing of emotional words revealed in temporoparietal junctions of both hemispheres by EEG and TMS.

We investigate the contribution of both hemispheres in a lateralised lexical decision paradigm with emotional and neutral words in healthy volunteers. In a first experiment, high-density EEG analysis using source imaging methods revealed early specific participation of the temporoparietal junctions (TPJ) in both hemispheres for the detection of words. Then, in an event-related transcranial magnetic stimulation experiment with the same task, the disruption of left or right TPJ compared with a control stimulation over the vertex showed a slowing that is more pronounced when words are emotional and presented in the left visual field (LVF).

Hemispheric specialization varies with EEG brain resting states and phase of menstrual cycle.

A growing body of behavioral studies has demonstrated that women's hemispheric specialization varies as a function of their menstrual cycle, with hemispheric specialization enhanced during their menstruation period. Our recent high-density electroencephalogram (EEG) study with lateralized emotional versus neutral words extended these behavioral results by showing that hemispheric specialization in men, but not in women under birth-control, depends upon specific EEG resting brain states at stimulus arrival, suggesting that hemispheric specialization may be pre-determined at the moment of the stimulus onset. To investigate whether EEG brain resting state for hemispheric specialization could vary as a function of the menstrual phase, we tested 12 right-handed healthy women over different phases of their menstrual cycle combining high-density EEG recordings and the same lateralized lexical decision paradigm with emotional versus neutral words.

An LCD tachistoscope with submillisecond precision.

Tachistoscopes allow brief visual stimulation delivery, which is crucial for experiments in which subliminal presentation is required. Up to now, tachistoscopes have had shortcomings with respect to timing accuracy, reliability, and flexibility of use. Here, we present a new and inexpensive two-channel tachistoscope that allows for exposure durations in the submillisecond range with an extremely high timing accuracy.

Can postictal memory predict postoperative memory in patients with temporal lobe epilepsy?

We investigated the contribution of postictal memory testing for lateralizing the epileptic focus and predicting memory outcome after surgery for temporal lobe epilepsy (TLE). Forty-five patients with TLE underwent interictal, postictal, and postoperative assessment of verbal and nonverbal memory. Surgery consisted of anterior temporal lobectomy (36), selective isolated amygdalohippocampectomy (6), or amygdalohippocampectomy coupled to lesionectomy (3).

Crossed ataxia: a case report and a diffusion tensor imaging tractography study.

Background And Purpose: Ever since the seminal description of ataxic hemiparesis contralateral to a pontine lesion by Miller-Fisher, the question of why contralesional crossing pontocerebellar fibers do not more frequently produce ipsilesional hemiataxia was raised. The few cases of "quadrataxic hemiparesis" or bilateral leg ataxia remain exceptions.

Summary Of Case: We report an even more unusual variant, namely "crossed ataxia" of the contralesional arm and the ipsilesional leg subsequent to an anteromedial pontine ischemic stroke.

Simultaneous Doppelgänger and limb amputation impression in right frontal opercular stroke.

A case is described of a patient who presented almost simultaneously the impression that his left arm was amputated and the feeling of the presence of his invisible Doppelgänger. While these body scheme disorders have both been described after (right) parietal lesions, a right frontal opercular ischaemic stroke was found in the neurological work up. Diffusion tensor imaging showed that the stroke involved the ventral bundle of the superior longitudinal fasciculus that connects the parietal to the frontal lobe.

On the origin of the N400 effects: an ERP waveform and source localization analysis in three matching tasks.

The question of the cognitive nature and the cerebral origins of the event-related potential (ERP) N400 component has frequently been debated. Here, the N400 effects were analyzed in three tasks. In the semantic task, subjects decided whether sequentially presented word pairs were semantically related or unrelated.

The neural substrates and timing of top-down processes during coarse-to-fine categorization of visual scenes: a combined fMRI and ERP study.

Spatial frequencies in an image influence visual analysis across a distributed, hierarchically organized brain network. Low spatial frequency (LSF) information may rapidly reach high-order areas to allow an initial coarse parsing of the visual scene, which could then be "retroinjected" through feedback into lower level visual areas to guide finer analysis on the basis of high spatial frequency (HSF). To test this "coarse-to-fine" processing scheme and to identify its neural substrates in the human brain, we presented sequences of two spatial-frequency-filtered scenes in rapid succession (LSF followed by HSF or vice versa) during fMRI and ERPs in the same participants.

Electrical neuroimaging of single trials to identify laterality and brain regions involved in finger movements.

Thought-controlled neuroprostheses could allow paralyzed patients to interact with the external world using brain waves. Thus far, the fastest and more accurate control of neuroprostheses is achieved through direct recordings of neural activity [Nicolelis, M.A.

Differential impact of posterior lesions in the left and right hemisphere on visual category learning and generalization to contrast reversal.

Hemispheric differences in the learning and generalization of pattern categories were explored in two experiments involving sixteen patients with unilateral posterior, cerebral lesions in the left (LH) or right (RH) hemisphere. In each experiment participants were first trained to criterion in a supervised learning paradigm to categorize a set of patterns that either consisted of simple geometric forms (Experiment 1) or unfamiliar grey-level images (Experiment 2). They were then tested for their ability to generalize acquired categorical knowledge to contrast-reversed versions of the learning patterns.

Seeing the phantom: a functional magnetic resonance imaging study of a supernumerary phantom limb.

Objective: Supernumerary phantom limb (SPL) is a rare neurological manifestation where patients with a severe stroke-induced sensorimotor deficit experience the illusory presence of an extra limb that duplicates a real one. The illusion is most often experienced as a somesthetic phantom, but rarer SPLs may be intentionally triggered or seen. Here, we report the case of a left visual, tactile, and intentional SPL caused by right subcortical damage in a nondeluded woman.

Perceptual distortion in homonymous paracentral scotomas.

Background: Cortical remapping after peripheral or central visual deafferentation alters visual perception, but it is unclear whether such a phenomenon impinges on areas remote from a scotoma. To investigate this question, we studied variations of perceptual spatial distortion in the visual field of patients with homonymous paracentral scotoma.

Methods: Two patients with right inferior homonymous paracentral scotoma were asked to describe their perception of a series of figures showing two isometric vertical lines symmetrically located on either side of a fixation point.

Reversed flow in the external carotid artery despite a patent but stenosed common carotid artery.

Background And Purpose: Occlusion of the common carotid artery (CCA) is generally associated with an occlusion of the ipsilateral internal carotid artery (ICA) or of the external carotid artery (ECA) or of both. Sometimes, collateral circulation to the ECA may preserve patency of the ICA via retrograde perfusion through the bulb. We herewith report a case of reversed flow in the ECA in the presence of a patent but stenosed CCA as diagnosed with color-coded duplex flow imaging (CDFI).

Peripheral autoimmune neuropathy assessed using corneal in vivo confocal microscopy.

Background: Corneal nerves can be examined using in vivo confocal microscopy (IVCM). This new technique permits sequential observation of the corneal subbasal nerve plexus and detects early signs of diabetic peripheral neuropathy.

Objective: To describe a patient with autoimmune peripheral neuropathy followed up using corneal IVCM.

Levetiracetam accumulation in renal failure causing myoclonic encephalopathy with triphasic waves.

Triphasic waves are seen in the electro-encephalogram of adult patients with toxic-metabolic encephalopathies of various origins. Levetiracetam is a broad spectrum anti-epileptic drug with renal elimination and no hepatic metabolism. We describe the case of encephalopathy with triphasic waves concomitant with levetiracetam accumulation in a patient with chronic renal failure.