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

Effects of L-Dopa and Dopamine D2 Agonists on Recollection and Familiarity in Idiopathic Nondementing Parkinson’s Disease

Idiopathic nondementing Parkinson’s disease (PD) is marked by progressive loss of dopaminergic neurons in the substantia nigra pars compacta and ventral tegmental area. Recent brain imaging work implicates these structures in dopamine modulated networks subserving episodic memory. These findings are of relevance to PD because they suggest that dopamine depletion contributes to the disease-dependent decline in episodic memory, and therefore, this decline should, at least partially, be remediated by dopaminergic medication. Recognition memory (RM), recollection and familiarity during recognition was examined in 17 PD patients, 12 of whom were medicated with a D2 dopamine agonist (pramipexole or ropinirole) and l-dopa, with a further 5 PD control patients on l-dopa but no D2 agonist. Memory was tested “ON” and, following a period of medication withdrawal, “OFF” and compared to a group of 14 matched healthy volunteers (HV). The HVs were also tested twice in the absence of medication. The patients on the agonists PD showed significant impairments in recollection ON- and OFF-medication, whereas the l-dopa control patients exhibited a decline in OFF-recollection only. RM and familiarity were spared in both groups ON- and OFF-medication. These findings suggest that D2 dopamine agonists (combined with l-dopa) contribute to disease-dependent episodic memory impairment

A cognitive neuropsychological and psychophysiological investigation of a patient who exhibited an acute exacerbated behavioural response during innocuous somatosensory stimulation and movement.

We report findings from a cognitive neuropsychological and psychophysiological investigation of a patient who displayed an exacerbated acute emotional expression during movement, innocuous, and aversive somatosensory stimulation. The condition developed in the context of non-specific white matter ischaemia along with abnormalities in the cortical white matter of the left anterior parietal lobe, and subcortical white matter of the left Sylvian cortex. Cognitive neuropsychological assessment revealed a pronounced deficiency in executive function, relative to IQ, memory, attention, language and visual processing. Compared to a normal control group, the patient [EQ] displayed a significantly elevated skin conductance level during both innocuous and aversive somatosensory stimulation. His pain tolerance was also significantly reduced. Despite this, EQ remained able to accurately describe the form of stimulation taking place, and to rate the levels of pain intensity and pain affect. These results suggest that EQ's exaggerated behavioural response and reduced pain tolerance to somatosensory stimulation may be linked to cognitive changes, possibly related to increased apprehension and fear, rather than altered pain intensity or pain affect per se

The role of reality monitoring in anosognosia for hemiplegia.

Background: The aim was to assess the feasibility of a single-centre, single-blind, randomized, crossover design to explore the effects of two slow-release dopamine agonists, ropinirole and pramipexole, on cued recall in Parkinson’s disease.As the design required a switch from the prescribed agonist (pramipexole-to-ropinirole, or ropinirole-to-pramipexole), the primary objectives were to (a) examine the efficacy of processes and procedures used to manage symptoms during the washout period and (b) to use cued recall estimates to inform a power calculation for a definitive trial.Secondary objectives were to assess consent and missing data rates, acceptability of clinical support for the OFF sessions, experience of the OFF sessions and of agonist switching, barriers-to-participation for patients and informal caregivers.Methods: Patients were randomized in a 1:1 ratio to two treatment arms and stabilized on each agonist for 6 weeks. The arms differed only in the sequence in which the agonists were administered. Cued recall was assessed ON medication and, following a washout period resulting in 93.75% agonist elimination, OFF medication.Results: A total of 220 patients were screened: 145 were excluded and 75 invitations to participate were sent to eligible patients. Fifty-three patients declined, 22 consented and 16 completed the study.There were no serious adverse events, and rates of non-serious adverse events were equivalent between the agonists.Using the largest standard deviation (SD) of the ON–OFF difference cued recall score (inflated by ~25% to give aconservative estimate of the SD in a definitive trial) and assuming an effect of at least 10% of the observed range of OFF medication cued recall scores for either agonist to be clinically important, a main trial requires a sample size of just under 150 patients.The consent and missing data rates were 29 and 27% respectively. The washout period and the preparation for the OFF sessions were acceptable, and the sessions were manageable. The experience of switching was also manageable. Barriers to participation included concerns about disease stability, side effects, research process, carer workload and accessibility of the information sheet.Conclusions: This study presented challenges to recruitment both in design and execution, and while it was a major aim of the study to assess this, evaluation of these challenges provided the opportunity to explore how they could be overcome for future studies