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

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

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

Second-generation dopamine agonists and recollection impairments in Parkinson's disease

A selective deficit in the recollection of episodic details is frequently reported in Parkinson's disease (PD). Previous explanations implicate dopamine dysregulation in prefrontal structures on which strategic memory processes rely. However, neuroimaging advancements suggest dopaminergic dysregulation of hippocampally dependent memory processes. Accordingly, dopamine agonists, which target D3 receptors in the hippocampus, may impair hippocampal functioning, causing a more pronounced recollection decline. Recognition memory (RM), familiarity, and recollection were examined in 21 patients with mild-to-moderate PD (Hoehn and Yahr mean: 2.67). Patients were subdivided into two subgroups according to dopamine agonist (pramipexole [PPX] or ropinirole [RPR]), and completed matched versions of an RM test in a medicated and unmedicated condition (termed ON and OFF, respectively). Ten demographically matched healthy volunteers (HVs) also completed both RM tasks in two separate sessions. The PD group (PPX and RPR subgroups combined) showed impairments in RM and recollection, but spared familiarity. When subdivided by dopamine agonist, the PPX subgroup's ON-medication recollection performance was significantly lower than that of both the HVs and RPR subgroup. There was no evidence of decline in OFF-medication recollection or familiarity in either the PPX or RPR subgroups. Recollection in both PD subgroups correlated positively with a composite measure of recall, but not prefrontally dependent measures of cognitive control. These findings suggest that mild-to-moderate PD patients may show relatively preserved recollection and familiarity, but that recollection is selectively disrupted by PPX, but not RPR and that this effect may depend on disrupted hippocampal function rather than impaired pre-frontally dependent executive functions

Visual object processing, reality monitoring, reasoning and visual hallucinations in Parkinson's disease

Up to 40% of patients with Parkinson’s disease will develop visual hallucinations at some point in their illness. Although medication, depression, duration of illness, and peripheral visual impairment have been identified as risk factors for hallucinations, more specific changes in cognitive function may also play a role. This pilot study evaluated 9 PD patients with visual hallucinations and 9 nonvisually-hallucinating PD patients on tests of imagery, recognition of objects, reasoning processes and reality monitoring. The reasoning processes tapped ability to derive a set of rules based on feedback, application of a strategy in relation to goal attainment and concept formation. Reality monitoring is defined as the normal process by which perceived and imagined events are discriminated in memory. In healthy volunteers, memories originating from experienced events have more contextual, perceptual and meaningful information than memories derived from internally generated events such as imagery processes, dreams and fantasies. However, if perceptual qualities of imagined events are unusually vivid, they may be more difficult to discriminate from perceived events. Our research revealed that visually hallucinating PD patients have greater difficulty with recognising visual objects viewed as either silhouettes (U=20.00, p=0.07) or when key identifying information which is hidden from view (U=22.00, p=0.05). Reasoning and reality monitoring processes were also deficient (both U=15.00, p=0.02). Errors in the reality monitoring task where most likely to occur for imagined items which were misattributed to perceived items. In contrast spatial processing, spatial imagery and visual object imagery showed higher levels of preservation. The findings from this study raise the possibility that visual hallucinations in PD could stem from a combination of impairments in visual object processing, particularly when key visual attributes of an item are obscured, reasoning and reality monitoring processes. Acknowledgements This work was supported by a Fasttrack grant from the Parkinson’s Disease Society