Chronic hematoma superimposed to a large frontotemporal arachnoid cyst: evidence against crowding of audioverbal memory.

We report a patient with a chronic subdural/epidural hematoma superimposed to a large arachnoid cyst occupying the left frontotemporal region. Both were discovered accidentally because of a trigeminal neuralgia and concomitant subjective memory complaints. Patient's sudden selective audioverbal memory impairment probably links to a primary cortical tone deregulation and expressed through deficits of arousal-mediating structures subtly impacted by the hematoma's progression. This case illustrates that in early-onset asymmetrical brain damage (usually left), language, audioverbal memory in particular, should not always come to dominate intact hemisphere function. A severity-threshold may exist below which inter-hemispheric reorganization of audioverbal memory is unlikely.

Selective impairment of auditory attention processing in idiopathic generalized epilepsies: Implications for their cognitive pathophysiology.

The neuropsychological characteristics of Idiopathic Generalized Epilepsies (IGEs) as a wide syndrome encompassing different clinical entities have been as yet not well understood. We have studied neuropsychological performance in patients suffering Juvenile Myoclonic Epilepsy (JME) and Generalized Tonic Clonic Seizures (IGE-GTCS-only) to provide indirect-cognitive evidence on the pathophysiology of IGE-related neuropsychological dysfunction. Greater arousal-related impairments were expected for the auditory modality, by drawing on previous anatomo-clinical and neuro-evolutionary accounts. We have studied neurocognitive functioning in 26 IGE patients, suffering either JME (n = 16) or IGE-GTCS-only (n = 10), and their healthy counterparts consisted of 26 (18 females) demographically matched participants. IGE patients (JME and IGE-GTCS-only) did worse with respect to HC (healthy controls) in visual- and auditory- speed of information processing (reaction time), auditory-vigilance and -response inhibition, visuo-motor coordination, visual working memory and motor speed, delayed visual recall, immediate- and delayed verbal episodic recall, lexical access and retrieval, semantic associative processing, auditory-verbal memory span and verbal learning. Although both IGE-GTCS-only and JME patients delayed episodic recall was defective, the former did significantly worse. We believe that IGE patients' neuropsychological derailments represent indirect-secondary manifestations of a primary cortical tone deregulation inherent to IGEs' pathophysiology. In particular, IGE patients' worse-dissociated performance in auditory TOVA-also seen previously in TBI and schizophrenia-may implicate a grater vulnerability of the auditory information processing system, as well as a possibly shared cognitive pathophysiological component between IGE and the above nosologies.

When having a limb means feeling overcomplete. Xenomelia, the chronic sense of disownership and the right parietal lobe hypothesis.

ABSTRACTXenomelia is a rare condition characterized by a persistent and intense desire for amputation of one or more healthy limbs. Some frequent clinical manifestations suggest the involvement of distinct neural substrates. Specifically, recent aetiopathological hypotheses about xenomelia propose a neurodevelopmental origin, highlighting the putative contribution of the right parietal lobe and right insula, known to subserve the construction of a coherent representation of the body as a whole. This literature review is aimed at analysing relevant findings about structural and functional brain correlates of xenomelia, focusing on the identification of key regions and their hemispheric distribution. Finally, implications about the potential link between xenomelia and phylogenetic development of the right parietal lobe are discussed. Despite a certain degree of heterogeneity and the spatial extension of networks involved, signs of partial right-sided lateralization of cortical nodes and left-sided lateralization of subcortical nodes emerged. Indeed, some areas-rsPL, riPL, PMC and rInsula-have been consistently found altered in xenomelia. In conclusion, the presence of both structural and functional multi-layered brain abnormalities in xenomelia suggests a multifactorial aetiology; however, as the prevalence of correlational studies, causal relationships remain to be investigated.

Prompting future events: Effects of temporal cueing and time on task on brain preparation to action.

Prediction about event timing plays a leading role in organizing and optimizing behavior. We recorded anticipatory brain activities and evaluated whether temporal orienting processes are reflected by the novel prefrontal negative (pN) component, as already shown for the contingent negative variation (CNV). Fourteen young healthy participants underwent EEG and fMRI recordings in separate sessions; they were asked to perform a Go/No-Go task in which temporal orienting was manipulated: the external condition (a visual display indicating the time of stimulus onset) and the internal condition (time information not provided). In both conditions, the source of the pN was localized in the pars opercularis of the iFg; the source of the CNV was localized in the supplementary motor area and cingulate motor area, as expected. Anticipatory activity was also found in the occipital-parietal cortex. Time on task EEG analysis showed a marked learning effect in the internal condition, while the effect was minor in the external condition. In fMRI, the two conditions had a similar pattern; similarities and differences of results obtained with the two techniques are discussed. Overall, data are consistent with the view that the pN reflects a proactive cognitive control, including temporal orienting.

Addressing Evidence Linking Secondary Alexithymia to Aberrant Humor Processing.

In this review, we explore current literature and assess evidence linking secondary (acquired) alexithymia to aberrant humor processing, in terms of their neurobiological underpinnings. In addition, we suggest a possible common neuropathological substrate between secondary alexithymia and deficits in humor appreciation, by drawing on neurophysiologic and neuroradiological evidence, as well as on a recent and unique single-case study showing the cooccurrence of secondary alexithymia and deficit in humor appreciation. In summary, what emerges from the literature is that the cortical midline structures, in particular the medial prefrontal cortex (mPFC), the anterior cingulate cortex (ACC), and the insular cortex, seem to play a crucial role in the expression of both alexithymia and defective humor processing, while though to a lesser extent, a right hemisphere and bilateral frontoparietal contribution becomes evident. Neurobiological evidence of secondary alexithymia and aberrant humor processing points to the putative role of ACC/mPFC and the insular cortex in representing crucial processing nodes whose damage may produce both the above clinical conditions. We believe that the association of secondary alexithymia and aberrant humor processing, especially humor appreciation deficit, and their correlation with specific brain regions, mainly ACG/mPFC, as emerged from the literature, may be of some heuristic importance. Increased awareness on this topic may be of aid for neurosurgeons when accessing emotion-relevant structures, as well as for neuropsychologists to intensify their efforts to plan evidence-based neurorehabilitative interventions to alleviate the deleterious effects of such interpersonal communication deficits.

Proactive Cortical Control in Spinal Cord Injury Subjects with Paraplegia.

Preparatory cortical activities were investigated in subjects with paraplegia attributed to spinal cord injury (SCI). Electroencephalogram (EEG) and behavioral data were recorded simultaneously in a visual-motor discrimination go/no-go task performed with the right upper limb. Eighteen SCI subjects participated to one, two, or three experimental sessions (Go/No-Go task), according to their availability and willingness to participate. To evaluate the effects of SCI on cortical activities as a function of time, we considered three SCI groups (9 individuals each), based on different time from the injury onset (acute, 1-2 months; subacute, 3-5 months; chronic, 6-9 months), and a control group of 9 healthy participants matched for age and sex. Results indicate that response time (RT) was slower and percentage of omissions was higher in SCI subjects than healthy, independently from time from lesion (TFL). Also, the proactive motor preparation, indexed by the Bereitschafts potential (BP), and the pre-frontal cognitive control, indexed by the pre-frontal negativity component, showed reduced amplitude in SCI subjects, independently from TFL. Conversely, TFL effect was observed in the BP topography, which showed a more posterior focus in subacute and chronic groups than healthies. Interestingly, despite this posteriorization, BP amplitudes maintained the well-known correlation with RTs. Overall, SCI affects cortical reorganization independently from TFL, regarding proactive activities for action inhibition and reaction time; conversely, a TFL effect was observed in the topography changes related to the cortical areas involved in proactive motor activity. Present data are in line with growing evidence of brain changes after SCI, in particular focusing on cognitive effects and evidencing possible functional mechanisms related to motor and cognitive readiness processing, relevant for SCI rehabilitation programs.

Emotional asymmetries in refractory medial temporal and frontal lobe epilepsy: Their impact on predicting lateralization and localization of seizures.

BACKGROUND: Emotional disturbances have been reported in patients with epilepsy. Although conflicting results emanate from relevant studies, depressive symptoms are seen more often in temporal lobe epilepsy (TLE) whereas, hypomanic/manic symptoms usually accompany frontal lobe epilepsy (FLE); the above psychiatric symptoms are especially seen in refractory epilepsy. However, neocortical TLE and medial TLE are considered as distinct epileptic syndromes, and there is limited literature on comparison of affective traits in medial TLE (MTLE) and FLE. AIM: In the present study, we sought to investigate affective traits among epilepsy surgery candidates suffering refractory left medial TLE (LMTLE), right medial TLE (RMTLE), left FLE (LFLE), and right FLE (RFLE). RESULTS: Our results revealed that patients with MTLE scored significantly higher than the ones with FLE in depression, anxiety, asthenia, and melancholia as measured by the Symptoms Rating Scale for Depression and Anxiety (SRSDA), while patients with FLE scored significantly higher in mania than those with MTLE. Moreover, patients with MTLE scored significantly higher than their FLE counterparts on the anxiety scale of the State Trait Personality Inventory (STPI)-trait version. When laterality of the seizure focus was taken into account, no differences were found among both patients with MTLE and patients with FLE, with exception for the Trail Making Test part B (TMT-B) in which patients with RMTLE performed significantly worse than patients with LMTLE. Seizure frequency was higher for FLE. CONCLUSIONS: We provide evidence for an anterior-frontal versus a posterior-medial temporal cerebral functional asymmetry with regard to the manifestation of manic and depressive emotional traits in FLE and MTLE, respectively. Our results are mainly discussed within the frame of their contribution in localizing and to a lesser extent in lateralizing seizures foci in epilepsy surgery candidates. We suggest that this is of great importance in the context of preoperative monitoring of epilepsy surgery, especially when neuropsychologists are called upon to provide anatomical information in defining the functional deficit zone.

Phantom limb sensations in the ear of a patient with a brachial plexus lesion.

Referred phantom sensations are frequently reported following a peripheral injury. However, very few cases describe such sensations of the ear, and it remains unclear how the aural nerve territory can be remapped to one specific peripheral nerve region. We report on a patient with brachial plexus avulsion who underwent sensory testing and was asked to report the location of the stimulated site and any other sensations experienced. The patient spontaneously described the sensation of his arm being separate from his body. Despite visual input, he felt that his fist was closed, with his thumb pointing inward. Importantly, he felt clear and reproducible sensations from the affected arm when the ipsilateral ear was touched. These referred sensations were noted just 15 days after sustaining the injury. The arm nerve territory was systematically remapped to a specific aural nerve territory by applying both manual and electrical stimulation. Stimulation of the external ear, which is innervated by the vagus nerve, showed high spatial specificity for the dorsal and volar skin surfaces of the limb, and clearly delineated digits. Somatosensory-evoked potentials indicated that cortical adaptation in the somatosensory stream transferred a spatially organized map of the limb to the skin of the outer ear. This referral of sensations to the ear, as distinct from the face, provides evidence of highly specific topographical reorganization of the central nervous system following peripheral injury. Rapid map changes in the phantom sensation to the ear as a function of stimulation of vagus nerve suggest that the reorganization process can occur in cortex rather than in the brainstem.

Potential implications of Luria's work for the neuropsychology of epilepsy and epilepsy surgery: A perspective for re-examination.

The pioneeristic work of Alexander Romanovic Luria into the field of human neuropsychology offered eminent contributions to clinical praxis by providing theory guided methods and instruments for the study of higher cortical functions. However, lots of this knowledge corpus either remains untranslated and thus inaccessible, or in some cases selectively overlooked by academic authorities and consequently not passed to the future generations of experts. Although Luria was not exclusively devoted to the study of epilepsy, his theories and clinical approaches actually penetrate the whole neuropathology spectrum. His holistic and systemic approach to the brain sounds nowadays more than opportune and consistent with the network approach of the modern neuroimaging era. As to epilepsy, the logic underlying the Lurian approach (cognitive functions organized into complex functional systems with intra- and/or inter-hemispheric distribution, as opposed to the modularistic view of the brain) seems consistent with our current knowledge in epileptology with respect to epileptic networks, as well as the modern construct of the functional deficit zone. These contributions seem to be highly promising for the neuropsychology of epilepsy and epilepsy surgery, since they provide clinicians with valuable methods and theories to assist them in the localization -and lateralization- of cognitive deficits. Consequently they are of great applicability in the context of the preoperative neuropsychological monitoring of patients candidates for epilepsy surgery, where neuropsychologist are called upon to provide surgeons with anatomical data.

Hemispheric asymmetries in the transition from action preparation to execution.

Flexible and adaptive behavior requires the ability to contextually stop inappropriate actions and select the right one as quickly as possible. Recently, it has been proposed that three brain regions, i.e., the inferior frontal gyrus (iFg), the anterior insula (aIns), and the anterior intraparietal sulcus (aIPs), play an important role in several processing phases of perceptual decision tasks, especially in the preparation, perception and action phases, respectively. However, little is known about hemispheric differences in the activation of these three areas during the transition from perception to action. Many studies have examined how people prepare to stop upcoming responses through both proactive and reactive inhibitory control. Although inhibitory control has been associated with activity in the right prefrontal cortex (PFC), we have previously reported that, during a discriminative response task performed with the right hand, we observed: 1) a bilateral activity in the iFg during the preparation phase, and 2) a left dominant activity in the aIns and aIPs during the transition from perception to action, i.e., the so-called stimulus-response mapping. To clarify the hemispheric dominance of these processes, we combined the high temporal resolution of event-related potentials (ERPs) with the high spatial resolution of event-related functional magnetic resonance imaging (fMRI) while participants performed a discriminative response task (DRT) and a simple response task (SRT) using their non-dominant left hand. We confirmed that proactive inhibitory control originates in the iFg: its activity started one second before the stimulus onset and was released concomitantly to the stimulus appearance. Most importantly, we confirmed the presence of a bilateral iFg activity that seems to reflect a bilateral proactive control rather than a right-hemisphere dominance or a stronger control of the hemisphere contralateral to the responding hand. Further, we observed a stronger activation of the left aIns and a right-lateralized activation of the aIPs reflecting left-hemisphere dominance for stimulus-response mapping finalized to response execution and a contralateral-hand parietal premotor activity, respectively.

Possible common neurological breakdowns for alexithymia and humour appreciation deficit: A case study.

This brief work is an attempt to point to the possible common neurological breakdowns in giving rise to alexithymia, and impaired appreciation of humour. In particular, we present the case of a patient who lost the ability to enjoy humour after the surgical removal of a frontal groove meningioma, although he was still able to detect it, while at the same time was diagnosed with organic alexithymia. Our results indicate that problems in the affective appreciation of humour and in emotionalizing (alexithymic symptoms) may be the result of damage to the ventral-rostral portions of the ACG/mPFC, which prevent the patient from assessing the salience of emotion and motivational information, and generating emotional reactions; as a result he has trouble experiencing emotions, knowing how he and others feel, and enjoy humour.

How the brain prevents a second error in a perceptual decision-making task.

In cognitive tasks, error commission is usually followed by a performance characterized by post-error slowing (PES) and post-error improvement of accuracy (PIA). Three theoretical accounts were hypothesized to support these post-error adjustments: the cognitive, the inhibitory, and the orienting account. The aim of the present ERP study was to investigate the neural processes associated with the second error prevention. To this aim, we focused on the preparatory brain activities in a large sample of subjects performing a Go/No-go task. The main results were the enhancement of the prefrontal negativity (pN) component -especially on the right hemisphere- and the reduction of the Bereitschaftspotential (BP) -especially on the left hemisphere- in the post-error trials. The ERP data suggested an increased top-down and inhibitory control, such as the reduced excitability of the premotor areas in the preparation of the trials following error commission. The results were discussed in light of the three theoretical accounts of the post-error adjustments. Additional control analyses supported the view that the adjustments-oriented components (the post-error pN and BP) are separated by the error-related potentials (Ne and Pe), even if all these activities represent a cascade of processes triggered by error-commission.

Spatiotemporal brain mapping during preparation, perception, and action.

Deciding whether to act or not to act is a fundamental cognitive function. To avoid incorrect responses, both reactive and proactive modes of control have been postulated. Little is known, however, regarding the brain implementation of proactive mechanisms, which are deployed prior to an actual need to inhibit a response. Via a combination of electrophysiological and neuroimaging measures (recorded in 21 and 16 participants, respectively), we describe the brain localization and timing of neural activity that underlies the anticipatory proactive mechanism. From these results, we conclude that proactive control originates in the inferior Frontal gyrus, is established well before stimulus perception, and is released concomitantly with stimulus appearance. Stimulus perception triggers early activity in the anterior insula and intraparietal cortex contralateral to the responding hand; these areas likely mediate the transition from perception to action. The neural activities leading to the decision to act or not to act are described in the framework of a three-stage model that includes perception, action, and anticipatory functions taking place well before stimulus onset.

Stimulus onset predictability modulates proactive action control in a Go/No-go task.

The aim of the study was to evaluate whether the presence/absence of visual cues specifying the onset of an upcoming, action-related stimulus modulates pre-stimulus brain activity, associated with the proactive control of goal-directed actions. To this aim we asked 12 subjects to perform an equal probability Go/No-go task with four stimulus configurations in two conditions: (1) uncued, i.e., without any external information about the timing of stimulus onset; and (2) cued, i.e., with external visual cues providing precise information about the timing of stimulus onset. During task both behavioral performance and event-related potentials (ERPs) were recorded. Behavioral results showed faster response times in the cued than uncued condition, confirming existing literature. ERPs showed novel results in the proactive control stage, that started about 1 s before the motor response. We observed a slow rising prefrontal positive activity, more pronounced in the cued than the uncued condition. Further, also pre-stimulus activity of premotor areas was larger in cued than uncued condition. In the post-stimulus period, the P3 amplitude was enhanced when the time of stimulus onset was externally driven, confirming that external cueing enhances processing of stimulus evaluation and response monitoring. Our results suggest that different pre-stimulus processing come into play in the two conditions. We hypothesize that the large prefrontal and premotor activities recorded with external visual cues index the monitoring of the external stimuli in order to finely regulate the action.

Towards multiple interactions of inner and outer sensations in corporeal awareness.

Under normal circumstances, different inner- and outer-body sources are integrated to form coherent and accurate mental experiences of the state of the body, leading to the phenomenon of corporeal awareness. How these processes are affected by changes in inner and outer inputs to the body remains unclear. Here, we aim to present empirical evidence in which people with a massive sensory and motor disconnection may continue to experience feelings of general body state awareness without complete control of their inner and outer states. In these clinical populations, the activity of the neural structures subserving inner and outer body processing can be manipulated and tuned by means of body illusions that are usually based on multisensory stimulation. We suggest that a multisensory therapeutic approach could be adopted in the context of therapies for patients suffering from deafferentation and deefferentation. In this way, these individuals could regain a more complete feeling and control of the sensations they experience, which vary widely depending on their neurological condition.

Why do we make mistakes? Neurocognitive processes during the preparation-perception-action cycle and error-detection.

The event-related potential (ERP) literature described two error-related brain activities: the error-related negativity (Ne/ERN) and the error positivity (Pe), peaking immediately after the erroneous response. ERP studies on error processing adopted a response-locked approach, thus, the question about the activities preceding the error is still open. In the present study, we tested the hypothesis that the activities preceding the false alarms (FA) are different from those occurring in the correct (responded or inhibited) trials. To this aim, we studied a sample of 36 Go/No-go performers, adopting a stimulus-locked segmentation also including the pre-motor brain activities. Present results showed that neither pre-stimulus nor perceptual activities explain why we commit FA. In contrast, we observed condition-related differences in two pre-response components: the fronto-central N2 and the prefrontal positivity (pP), respectively peaking at 250 ms and 310 ms after the stimulus onset. The N2 amplitude of FA was identical to that recorded in No-go trials, and larger than Hits. Because the new findings challenge the previous interpretations on the N2, a new perspective is discussed. On the other hand, the pP in the FA trials was larger than No-go and smaller than Go, suggesting an erroneous processing at the stimulus-response mapping level: because this stage triggers the response execution, we concluded that the neural processes underlying the pP were mainly responsible for the subsequent error commission. Finally, sLORETA source analyses of the post-error potentials extended previous findings indicating, for the first time in the ERP literature, the right anterior insula as Pe generator.