Neuroanatomical segregation of texture-sensitivity in feline striate cortex

Recordings were obtained from striate cortical neurones in cats lightly anaesthetized with nitrous oxide/oxygen supplemented with halothane as necessary: muscle relaxant (gallamine triethiodide) was administered intravenously. Complex neurones were subdivided on the basis of their length summating properties for an optimally oriented bar into "standard", "special" or "intermediate" categories, and on their degree of sensitivity to motion of random texture into weakly and strongly texture-sensitive categories. In addition, a range of receptive field properties were compared, which included directional and orientational selectivity; end-stopping; receptive field dimensions; ocular dominance; and resting discharge levels. These properties were related to both neuronal class (simple or complex) and to the "special" and "standard" subdivisions of the complex neurone category ("intermediate" complex neurones were excluded from further analysis due to lack of numbers). Extracel1ular recordings were made from single neurones, with micropipettes filled with 12"/. East Green FCF in 2M sodium chloride. Extracellular dye-marks were made at the site of recording from each strongly texture-sensitive complex neurone. Microelectrode tracks were reconstructed with the aid of histologically recovered identifying dye-marks, in sections which had been counterstained with cresyl violet to reveal cortical lamination. This enabled calculation of brain shrinkage, and also labelled the layers containing the strongly texture-sensitive complex neurones. Under deep anaesthesia, animals were terminally perfused with phosphate-buffered saline (1 litre at 38 degrees Centigrade: pH 7.3) followed by 1 litre of IV, glutaraldehyde and 37. formaldehyde fixative. This study provides direct anatomical confirmation of the inference made by Hammond it MacKay ('75, ’77), and the 2-deoxyglucose studies by Wagner, Hoffmann and Zwerger ('81), that strongly texture-sensitive complex neurones lie in two bands, a superficial band in lower layer III, extending down into upper layer IV and a deeper band in layer V. A population of standard complex neurones, resident in both bands, was found to be strongly texture-sensitive, whilst strongly texture-sensitive special complex neurones were restricted to the deeper band in layer V

Motor versus body awareness: Voxel-based lesion analysis in anosognosia for hemiplegia and somatoparaphrenia following right hemisphere stroke

This is the accepted manuscript version of the following article: Valentina Moro, Simone Pernigo, Manos Tsakiris, Renato Avesani, Nicola M. J. Edelstyn, Paul M. Jenkinson, and Aikaterini Fotopoulou, ‘Motor versus body awareness: Voxel-based lesion analysis in anosognosia for hemiplegia and somatoparaphrenia following right hemisphere stroke’, Cortex, Vol 83, pp. 62-77, first published online 15 Jul 2016. The version of record is available online at doi: http://dx.doi.org/10.1016/j.cortex.2016.07.001 Published by Elsevier. © Elsevier Ltd. All rights reserved.Anosognosia for hemiplegia (AHP) is informative about the neurocognitive basis of motor awareness. However, it is frequently associated with concomitant symptoms, such as hemispatial neglect and disturbances in the sense of body ownership (DSO). Although double dissociations between these symptoms have been reported, there is ongoing debate about whether they are manifestations of independent abnormalities, or a single neuro- cognitive deficit. We aimed to investigate the specificity of lesions associated with AHP by surpassing four, existing methodological limitations: (a) recruit a relatively large sample of patients (total N 1⁄4 70) in a multi-centre study; (b) identify lesions associated with AHP in grey and white matter using voxel-based methods; (c) take into account the duration of AHP and concomitant neglect symptoms; and (d) compare lesions against a control hemiplegic group, patients suffering from AHP and DSO, and a few, rare patients with selective DSO. Results indicated that acute AHP is associated with a wide network, mainly including: (1) the Rolandic operculum, (2) the insula and (3) the superior temporal gyri. Subcortically, damage mainly involved the basal ganglia and white matter, mostly the superior corona radiate, arcuate fasciculus and the part of the ventral, superior longitu- dinal fasciculus. Persistent symptoms were linked with wider damage involving fronto- temporal cortex and long white matter tracts. A shift in the latero-medial direction (mainly involving the basal ganglia and surrounding white matter) emerged when DSO was taken accounted for. These results suggest that while bodily awareness is processed by areas widely distributed across the brain, intact subcortical structures and white matter tracts may be necessary to support basic feelings of owning and controlling contralateral body parts. An accurate and ‘up-to-date’ awareness of our motor abilities, however, may rely also on intact processing in cortical areas which presumably allow higher-order in- ferences about the current state of the body.Peer reviewedFinal Accepted Versio

Impulse Control Disorder in Parkinson's Disease: A Meta-Analysis of Cognitive, Affective, and Motivational Correlates

Background: In Parkinson's disease (PD), impulse control disorders (ICDs) develop as side-effect of dopaminergic replacement therapy (DRT). Cognitive, affective, and motivational correlates of ICD in medicated PD patients are debated. Here, we systematically reviewed and meta-analyzed the evidence for an association between ICD in PD and cognitive, affective, and motivational abnormalities.Methods: A systematic review and meta-analysis was performed on PubMed, Science Direct, ISI Web of Science, Cochrane, EBSCO for studies published between 1-1-2000 and 8-3-2017 comparing cognitive, affective, and motivational measures in PD patients with ICD (ICD+) vs. those without ICD (ICD–). Exclusion criteria were conditions other than PD, substance and/or alcohol abuse, dementia, drug naïve patients, cognition assessed by self-report tools. Standardized mean difference (SMD) was used, and random-effect model applied.Results: 10,200 studies were screened (title, abstract), 79 full-texts were assessed, and 25 were included (ICD+: 625 patients; ICD–: 938). Compared to ICD–, ICD+ showed worse performance reward-related decision-making (0.42 [0.02, 0.82], p = 0.04) and set-shifting tasks (SMD = −0.49 [95% CI −0.78, −0.21], p = 0.0008). ICD in PD was also related to higher self-reported rate of depression (0.35 [0.16, 0.54], p = 0.0004), anxiety (0.43 [0.18, 0.68], p = 0.0007), anhedonia (0.26 [0.01, 0.50], p = 0.04), and impulsivity (0.79 [0.50, 1.09], p < 0.00001). Heterogeneity was low to moderate, except for depression (I2 = 61%) and anxiety (I2 = 58%).Conclusions: ICD in PD is associated with worse set-shifting and reward-related decision-making, and increased depression, anxiety, anhedonia, and impulsivity. This is an important area for further studies as ICDs have negative impact on the quality of life of patients and their caregivers

Dopaminergic Neurotransmission in Patients With Parkinson's Disease and Impulse Control Disorders: A Systematic Review and Meta-Analysis of PET and SPECT Studies

Background: Around 30% Parkinson's disease (PD) patients develop impulse control disorders (ICDs) to D2/3 dopamine agonists and, to a lesser extent, levodopa. We aim to investigate striatal dopaminergic function in PD patients with and without ICD.Methods: PubMed, Science Direct, EBSCO, and ISI Web of Science databases were searched (from inception to March 7, 2018) to identify PET or SPECT studies reporting striatal dopaminergic function in PD patients with ICD (ICD+) compared to those without ICD (ICD–). Studies which included drug naïve patients, explored non-pharmacological procedures (e.g., deep brain stimulation), and those using brain blood perfusion or non-dopaminergic markers were excluded. Standardized mean difference (SDM) was used and random-effect models were applied. Separate meta-analyses were performed for dopamine transporter level, dopamine release, and dopamine receptors availability in the putamen, caudate, dorsal, and ventral striatum.Results: A total of 238 studies were title and abstract screened, of which 19 full-texts were assessed. Nine studies (ICD+: N = 117; ICD–: N = 175 patients) were included in the analysis. ICD+ showed a significant reduction of dopamine transporter binding in the putamen (SDM = −0.46; 95% CI: −0.80, −0.11; Z = 2.61; p = 0.009), caudate (SDM = −0.38; 95% CI: −0.73, −0.04; Z = 2.18; p = 0.03) and dorsal striatum (SDM = −0.45; 95% CI: −0.77, −0.13; Z = 2.76; p = 0.006), and increased dopamine release to reward-related stimuli/gambling tasks in the ventral striatum (SDM = −1.04; 95% CI: −1.73, −0.35; Z = 2.95; p = 0.003). Dopamine receptors availability did not differ between groups. Heterogeneity was low for dopamine transporter in the dorsal striatum (I2 = 0%), putamen (I2 = 0%) and caudate (I2 = 0%), and pre-synaptic dopamine release in the dorsal (I2 = 0%) and ventral striatum (I2 = 0%); heterogeneity was high for dopamine transporter levels in the ventral striatum (I2 = 80%), and for dopamine receptors availability in the ventral (I2 = 89%) and dorsal (I2 = 86%) striatum, putamen (I2 = 93%), and caudate (I2 = 71%).Conclusions: ICD+ patients show lower dopaminergic transporter levels in the dorsal striatum and increased dopamine release in the ventral striatum when engaged in reward-related stimuli/gambling tasks. This dopaminergic imbalance might represent a biological substrate for ICD in PD. Adequately powered longitudinal studies with drug naïve patients are needed to understand whether these changes may represent biomarkers of premorbid vulnerability to ICD

Major depressive disorder and schizophrenia are associated with a disturbed experience of temporal memory

Background Disturbances in ‘psychological time’ are frequently reported in major depressive disorder (MDD) and schizophrenia. If one accepts the suggestion that the experience of the dimensions of time, past-present-future, are not inseparable then a disturbance in episodic memory is implicated. Episodic memory allows us to make sense of the world and our place within it by constructing a temporal context and temporal flow between events. These temporal representations are disordered in schizophrenia, but whether this is reflected in MDD is not known. Temporal-order memory deficits can be explained by two hypotheses. The prefrontal-organisational hypothesis suggests that deficits result from a breakdown in processes involved in encoding, retrieval, monitoring and decision-making. Whereas the hippocampal-mnemonic theory suggests that item-encoding, and inter-item associative encoding contribute to temporal-order memory. Methods New learning, recency judgments and executive function were investigated in 14 MDD patients, 15 schizophrenia patients and 10 healthy volunteers (HVs). Results Relative to HVs, both MDD and schizophrenia made more temporal errors despite achieving 100% learning. Deficits in executive function and item-recognition were present in both psychiatric groups, but executive function correlated to temporal errors in MDD only, and item-recognition to new learning in schizophrenia only. Limitations MDD and schizophrenia patients were taking medication Conclusions Temporal-ordering deficits are evident in both MDD and schizophrenia, and whilst the disruption of organisational and mnemonic processes appears to be ubiquitous, preliminary evidence from the correlational analysis suggests prefrontal problems are implicated in MDD temporal-order deficits, whereas hippocampal are more associated to temporal-order memory deficits in schizophrenia

Visual Hallucinations in Parkinson’s Disease: a Hierarchy of Impairments Involving Perception, Source Monitoring and Reasoning

Up to 45% of patients with Parkinson’s disease (PD) will develop visual hallucinations (VH) at some point in their illness. Although medication, depression, illness duration and ophthalmic abnormalities are identified as risk factors for VH-PD, specific perceptual and cognitive impairments may also play a role. The aim of this study was therefore to explore a hierarchy of low level perceptual processes, imagery and high level executive functions linked to reasoning in groups of VH and non VH PD. This study investigated 18 patients with non dementing idiopathic PD. Nine patients had a history of VH. The VH and non VH PD groups were matched for demographic (age, gender), neuropsychological (premorbid and current levels of functioning) and clinical characteristics (disease duration, motor symptom severity, daily levodopa medication) apart from presence of VH in the index group. The VH-PD and non VH PD groups completed tests of bottom-up object processing and recognition, visual imagery, and top-down executive functions such as response inhibition, response suppression, source monitoring and spatial and probabilistic reasoning. Compared to the non VH-PD group, VH-PD patients showed impairments in object perception and recognition impairments in cases when key identifying details were obscured. They also made more source misattribution errors, where self-generated images were misattributed to an external source. Finally, abnormalities in reasoning were evident. On the other hand, there were no differences between the VH-PD and non VH-PD groups on measures of visual perception using canonical views of objects, spatial perception, visual imagery, and other measures of executive function (initiation and suppression of responses, decision-making and self-monitoring). The findings are discussed in relation to models of delusion and hallucination formation

Does autonomic arousal distinguish good and bad decisions? Healthy individuals’ skin conductance reactivity during the Iowa Gambling Task

Original article can be found at: http://psycontent.metapress.com/ Copyright Hogrefe & HuberThe Somatic Marker Hypothesis (SMH) proposes that physiological feedback to the brain influences cognitive appraisal and decision-making; however, the strength of evidence in support of the SMH is equivocal. In this study we examined the validity of the SMH by measuring physiological arousal in a population of healthy individuals playing the Iowa Gambling Task (IGT); a computerised card game designed to assess real-life decisionmaking. We also aimed to clarify uncertainty regarding the influence of reinforcer type and impulsiveness to IGT performance and the SMH. Skin conductance level (SCL) and heart rate reactivity were measured in forty-one participants performing the IGT using either facsimile or real money. Participants were categorised as non-impaired or impaired on the basis of their IGT performance, and any differences in performance and physiological between groups were examined. Heart rate data did not reveal any effects. Robust differences in SCL reactivity during the task were not found between impaired and nonimpaired individuals; however, marginal SCL rises were observed when non-impaired individuals anticipated and received a reward from disadvantageous choices compared with advantageous ones. This effect was found only when using facsimile money and did not occur in impaired individuals, suggesting some effect of reinforcer type on physiological activity and performance, and a difference in the physiology of impaired and non-impaired individuals. No significant differences in impulsiveness were found between impaired and non-impaired individuals. The findings suggest that autonomic activity is independent of long-term good or bad decision-making, and may reflect differences between decks in the magnitude of gain and loss. It is concluded that further substantiating evidence is needed for the SMH to continue as an explanation for human decision-making.Peer reviewe

Asymptomatic biological parents of a patient with schizophrenia show impairments in recognition memory

Background: Recognition memory dysfunction has been frequently reported in schizophrenic populations, and has been linked with the development of delusions and thought disorder. A range of neuropsychological abnormalities have also been documented in the biological asymptomatic relatives of patients with schizophrenia; however, recognition memory has not been one of them. Aim: This study was carried out in order to investigate: (i) verbal and facial recognition memory in terms of accuracy and false alarm rates; and (ii) contributions from the episodic and semantic memory systems to recognition memory, in the biological asymptomatic parents of a reported schizophrenic patient and a set of male and female psychotic controls. Results: Gender differences failed to emerge between the psychotic controls on any of the recognition measures (discrimination accuracy, response bias, hit and false alarm rates, ‘remember’ and ‘know’ recognition memory decisions). However, there was evidence of recognition dysfunction in the female relative, and to a lesser extent, in the male. Both parent's recognition memory performance profiles were marked by a pathologically elevated false alarm rate, and an increased dependence ‘remember’ judgements, i.e. input from the episodic memory system, to drive recognition memory decisions. Conclusions: These findings are discussed in the context of models of episodic and semantic memory impairment in schizophrenia