What is a multisensory cortex? A laminar,connectional, and functional study of a ferret temporal cortical multisensory area

Now that examples of multisensory neurons have been observed across the neocortex, this has led to some confusion about the features that actually designate a region as “multisensory.” While the documentation of multisensory effects within many different cortical areas is clear, often little information is available about their proportions or net functional effects. To assess the compositional and functional features that contribute to the multisensory nature of a region, the present investigation used multichannel neuronal recording and tract tracing methods to examine the ferret temporal region: the lateral rostral suprasylvian sulcal area. Here, auditory-tactile multisensory neurons were predominant and constituted the majority of neurons across all cortical layers whose responses dominated the net spiking activity of the area. These results were then compared with a literature review of cortical multisensory data and were found to closely resemble multisensory features of other, higher-order sensory areas. Collectively, these observations argue that multisensory processing presents itself in hierarchical and area-specific ways, from regions that exhibit few multisensory features to those whose composition and processes are dominated by multisensory activity. It seems logical that the former exhibit some multisensory features (among many others), while the latter are legitimately designated as “multisensory.”     

Is the ferret a suitable species for studying perinatal brain injury?

Complications of prematurity often disrupt normal brain development and/or cause direct damage to the developing brain, resulting in poor neurodevelopmental outcomes. Physiologically relevant animal models of perinatal brain injury can advance our understanding of these influences and thereby provide opportunities to develop therapies and improve long-term outcomes. While there are advantages to currently available small animal models, there are also significant drawbacks that have limited translation of research findings to humans. Large animal models such as newborn pig, sheep and nonhuman primates have complex brain development more similar to humans, but these animals are expensive, and developmental testing of sheep and piglets is limited. Ferrets (Mustela putorius furo) are born lissencephalic and undergo postnatal cortical folding to form complex gyrencephalic brains. This review examines whether ferrets might provide a novel intermediate animal model of neonatal brain disease that has the benefit of a gyrified, altricial brain in a small animal. It summarizes attributes of ferret brain growth and development that make it an appealing animal in which to model perinatal brain injury. We postulate that because of their innate characteristics, ferrets have great potential in neonatal neurodevelopmental studies.     

Is the avian hippocampus a functional homologue of the mammalian hippocampus?

The effects of hippocampal lesions on the processing and retention of visual and spatial information in birds and mammals is reviewed. Both birds and mammals with damage to the hippocampus are severely impaired on a variety of spatial tasks, such as navigation, maze learning, and the retention of spatial information. In contrast, both birds and mammals with damage to the hippocampus are not impaired on a variety of visual tasks, such as delayed matching-to-sample, concurrent discrimination, or retention of a visual discrimination. In addition, both birds and mammals with hippocampal damage display impairments in the acquisition of an autoshaped response, as well as alterations in response suppression. These findings suggest that the avian hippocampus is a functional homologue of the mammalian hippocampus, and that in both birds and mammals the hippocampus is important for the processing and retention of spatial, rather than purely visual information.     

The hippocampus and inhibitory learning: a 'Gray' area?

Gray's approach to understanding hippocampal functioning [The Neuropsychology of Anxiety: An Enquiry into the Function of the Septo-hippocampal System, 1982; The Neuropsychology of Anxiety, 2000] departs from the prevailing view of that structure as a substrate for memory. Instead, Gray and McNaughton have proposed that hippocampus is involved with a function that is more fundamental than memory, namely the resolution of conflict between competing approach and avoidance tendencies. The present paper attempts to advance this perspective by describing how the effects of selective lesions of the hippocampus on performance in both relatively simple Pavlovian conditioning tasks and in more complex radial maze problems could be a consequence of an impairment in a simple form of inhibitory learning. Specifically, we consider the idea that the hippocampus is needed to form simple inhibitory associations between events that are concurrently embedded in simple excitatory associations [Behav Brain Res 119 (2001) 111]. This idea is compared with the conflict resolution hypothesis offered by Gray and McNaughton and avenues of integration are noted. In addition, the potential role for inhibitory learning in hippocampal-dependent spatial and contextual information processing is also discussed.     

Warfarin for atrial fibrillation: the end of an era?

BACKGROUND: Warfarin has been in routine clinical use for more than 50 years; however, it was not proven to be of benefit in both primary and secondary prevention of stroke for patients with non-valvular atrial fibrillation (AF) until about a decade ago. Despite its efficacy in reducing the risk of stroke in patients with AF by about 60%, with an absolute reduction of about 3% per year, there have always been barriers to its use. These barriers have included the need for monitoring the degree of anticoagulation with blood tests to measure the international normalised ratio, frequent dose adjustments to maintain this ratio within quite a narrow therapeutic range, and the risk of bleeding should the upper limits of this range be exceeded. Aspirin has also been used but is less effective. RECENT DEVELOPMENTS: New oral drugs are being tested; these may be as effective at reducing stroke risk as warfarin in patients with AF. Direct thrombin inhibitors such as ximelagatran are not inferior to warfarin and, based on results from the SPORTIF III and V trials, are perhaps safer, with no need for long-term monitoring and dose adjustment. However, the side-effect of raised amounts of the liver enzyme alanine amino-transferase in 6% of patients needs to be resolved. In the ACTIVE trial, the efficacy of a combination of antiplatelet drugs (aspirin plus clopidogrel) is being tested against dose-adjusted warfarin; and in AMADEUS, the factor-Xa inhibitor and pentasaccharide idraparinux is being assessed in a similar way. Several surgical procedures and devices are also being developed to control AF rhythm and prevent stroke. WHERE NEXT?: The place of these new drugs in the management of AF needs to be established. In the short term, it seems that ximelagatran will replace warfarin in patients for whom there is evidence of a favourable risk-to-benefit ratio. The SPORTIF population consists of patients with AF plus at least one risk factor. More information about the effect of raised liver enzymes will probably not be available until phase IV studies are completed. Combination antiplatelet drugs need to be tested further--perhaps even triple therapy with aspirin, clopidogrel, and dipyridamole--if the results of ACTIVE are encouraging. The place of surgical procedures and devices to control rhythm and prevent stroke is unclear. Whatever happens, there is a high probability that the days of warfarin are numbered.     

The amygdala: is it an essential component of the neural network for social cognition?

Observations from human subjects with focal brain lesions and animal subjects with experimental lesions have implicated a variety of brain regions in the mediation of social behavior. Previous studies carried out in the macaque monkey found that lesions of the amygdala not only decrease emotional reactivity but also disrupt normal social interactions. We have re-investigated the relationship between amygdala lesions and social behavior in cohorts of mature and neonatal rhesus monkeys who were prepared with selective and complete bilateral ibotenic acid lesions of the amygdaloid complex. These animals display clear alterations in emotional and social behavior. We interpret these changes as due to a loss of the ability to evaluate environmental stimuli as potential threats. However, adult animals with bilateral lesions of the amygdala demonstrate near normal, and even increased, social interactions with conspecifics. Moreover, neonatal animals, prepared with amygdala lesions at 2 weeks of age, also demonstrate species typical social behaviors such as the generation of facial expressions, grooming and play behavior. These results argue against the idea that the amygdala is essential for the interpretation of social communication or for the expression of social behavior. Because it does appear to participate in the evaluation of the "safety" of social interactions, we believe that it does have a role in modulating the amount of social behavior in which an organism will participate. However, our current answer to the question posed in the title of this paper is no!     

The amygdala: is it an essential component of the neural network for social cognition?

Observations from human subjects with focal brain lesions and animal subjects with experimental lesions have implicated a variety of brain regions in the mediation of social behavior. Previous studies carried out in the macaque monkey found that lesions of the amygdala not only decrease emotional reactivity but also disrupt normal social interactions. We have re-investigated the relationship between amygdala lesions and social behavior in cohorts of mature and neonatal rhesus monkeys who were prepared with selective and complete bilateral ibotenic acid lesions of the amygdaloid complex. These animals display clear alterations in emotional and social behavior. We interpret these changes as due to a loss of the ability to evaluate environmental stimuli as potential threats. However, adult animals with bilateral lesions of the amygdala demonstrate normal, and even increased, social interactions with conspecifics. Moreover, neonatal animals, prepared with amygdala lesions at 2 weeks of age, also demonstrate species typical social behaviors such as the generation of facial expressions, grooming and play behavior. These results argue against the idea that the amygdala is essential for the interpretation of social communication or for the expression of social behavior. Because it does appear to participate in the evaluation of the "safety" of social interactions, we believe that it does have a role in modulating the amount of social behavior in which an organism will participate. However, our current answer to the question posed in the title of this paper is no!     

Ischemic stroke of the cortical “hand knob” area: stroke mechanisms and prognosis

Cortical ischemic stroke affecting the precentral “hand knob” area is a rare but well known stroke entity. To date, little is known about the underlying stroke mechanisms and the prognosis. Twenty-nine patients admitted to our service between 2003 and 2007 were included in the study on the basis of an acute ischemic infarct of the cortical “hand knob” area confirmed by diffusion-weighted magnetic resonance imaging with contralateral hand paresis. For all patients clinical, epidemiological as well as imaging data at the time point of admission were analysed retrospectively and follow-up data on all patients was obtained. The majority (n = 21/72%) had an isolated infarct of the cortical “hand knob” area. In 23 (79%) patients it was a first ever stroke. Ten patients (34%) had ipsilateral extracranial stenosis of the internal carotid artery (ICA), whereas potential cardiac embolic sources were less frequent (n = 4/14%). No patient exhibited ipsilateral MCA stenosis. All but two patients (93%) had marked atherosclerotic alterations of the ICA. Hypertension was the most prevalent vascular risk factor (n = 23/79%). At follow-up (mean 25.0 months, range 0.4–47.4 months) no patient had died and only one (3%) experienced a recurrent stroke. The majority of patients (79%) reported improvement of hand paresis, 17 (59%) were asymptomatic (modified Rankin score = 0). Only one patient was significantly disabled due to a recurrent stroke. In conclusion, ischemic infarcts affecting the cortical “hand knob” area are frequently associated with atherosclerotic changes of the carotid artery, suggesting an arterio-arterial thrombembolic stroke mechanism. It mostly reflects first ever ischemic stroke, and follow-up data suggest a rather benign course.     

The evolution of visual cortex: where is V2?

A comparative analysis of the area of the cortex that is adjacent to the primary visual area (V1), indicates that the lateral extrastriate cortex of primitive mammals was likely to contain only a single visuotopically organized field, the second visual area (V2). Few, if any, other visual areas existed. The opposing hypothesis, that primitive mammals had a 'string' of small visual areas in the cortex lateral to V1 (as in some rodents), is not supported by studies of the organization of extrastriate cortex in other mammals, nor by the variability in this organization among extant rodents. A critical re-analysis of published evidence on the presence of multiple areas adjacent to V1 in some rodents has led to alternative interpretations of the organization of the areas in these regions.     

The rat model of placental ischemia as a model of postpartum posterior cortical atrophy?

正Potential link between preeclampsia(PE)and posterior cortical atrophy(PCA):PCA is a neurodegenerative disorder affecting the parietal,occipital,and occipital-temporal brain regions,often manifesting as a decline in visual processing and perception skills in affected individuals.The most common underlying pathology of PCA     

Reduced cortical folding of the anterior cingulate cortex in obsessive–compulsive disorder

Background

Anterior cingulate cortex (ACC) abnormalities have been implicated consistently in the pathophysiology of obsessive–compulsive disorder (OCD), yet it remains unclear whether these abnormalities originated during early neurodevelopment. In this study, we examined the ACC sulcal/gyral patterns to investigate whether neurodevelopmental anomalies of the ACC were present in patients with OCD. We hypothesized that patients with OCD would show reduced cortical folding of the ACC compared with controls.

Methods

We used magnetic resonance imaging (MRI) of 169 healthy volunteers and 110 patients with OCD to examine the paracingulate sulcus and cingulate sulcus. We assessed cortical folding patterns according to established classification criteria and constructed 3 categories of paracingulate sulcus morphology according to its presence and anteroposterior extent: “prominent,” “present” and “absent.” We classified the cingulate sulcus as “interrupted” or “continuous” according to the interruptions in its course. In addition, we evaluated ACC sulcal asymmetry based on interhemispheric comparisons of paracingulate sulcus morphology.

Results

Analyses revealed that patients with OCD were significantly less likely than controls to show a well-developed left paracingulate sulcus: 50.0% of patients and 65.1% of controls showed a “prominent” or “present” paracingulate sulcus in the left hemisphere. However, there were no differences in regard to cingulate sulcus continuity, and patients also showed the same leftward ACC sulcal asymmetry as controls.

Limitations

Our study was limited by the fact that we obtained the MRI scans from 2 different scanners, and we did not calculate cerebral fissurization as our study was restricted to 1 specific brain region. Moreover, patients and controls differed significantly in terms of sex ratio and IQ, although we controlled these variables as covariates.

Conclusion

Our findings imply a subtle deviation in the early neurodevelopment of the ACC in patients with OCD, but the extent to which these anomalies contributed to the pathogenesis of OCD remains unclear. Further studies that link the ACC morphologic anomalies to the pathophysiology of OCD are recommended.     

Does the visual system of the flying fox resemble that of primates? The distribution of calcium-binding proteins in the primary visual pathway of Pteropus poliocephalus

It has been proposed that flying foxes and echolocating bats evolved independently from early mammalian ancestors in such a way that flying foxes form one of the suborders most closely related to primates. A major piece of evidence offered in support of a flying fox-primate link is the highly developed visual system of flying foxes, which is theorized to be primate-like in several different ways. Because the calcium-binding proteins parvalbumin (PV) and calbindin (CB) show distinct and consistent distributions in the primate visual system, the distribution of these same proteins was examined in the flying fox (Pteropus poliocephalus) visual system. Standard immunocytochemical techniques reveal that PV labeling within the lateral geniculate nucleus (LGN) of the flying fox is sparse, with clearly labeled cells located only within layer 1, adjacent to the optic tract. CB labeling in the LGN is profuse, with cells labeled in all layers throughout the nucleus. Double labeling reveals that all PV+ cells also contain CB, and that these cells are among the largest in the LGN. In primary visual cortex (V1) PV and CB label different classes of non-pyramidal neurons. PV+ cells are found in all cortical layers, although labeled cells are found only rarely in layer I. CB+ cells are found primarily in layers II and III. The density of PV+ neuropil correlates with the density of cytochrome oxidase staining; however, no CO+ or PV+ or CB+ patches or blobs are found in V1. These results show that the distribution of calcium-binding proteins in the flying fox LGN is unlike that found in primates, in which antibodies for PV and CB label specific separate populations of relay cells that exist in different layers. Indeed, the pattern of calcium-binding protein distribution in the flying fox LGN is different from that reported in any other terrestrial mammal. Within V1 no PV+ patches, CO blobs, or patchy distribution of CB+ neuropil that might reveal interblobs characteristic of primate V1 are found; however, PV and CB are found in separate populations of non-pyramidal neurons. The types of V1 cells labeled with antibodies to PV and CB in all mammals examined including the flying fox suggest that the similarities in the cellular distribution of these proteins in cortex reflect the fact that this feature is common to all mammals.     

A 10 Hz “alpha-like” rhythm in the visual cortex of the waking cat

Rhythms at about 10 Hz were recorded from the primary visual cortex of the cat (anterior part of area 18), with characteristics close to those of the alpha rhythm in man: frequency band (7–14 Hz), localization and reactivity to visual stimulation. Coherence analysis of this activity with the “mu” rhythms on the somatosensory cortex showed that although both types develop in the same overall behavioural situations (quiet waking and/or expectancy of an event to occur), they are independent.     

The value of therapeutic communities in the treatment of personality disorder: a suitable place for treatment?

In the United Kingdom, a government program investigating the links between offending and personality disorder has stimulated renewed interest in the treatment of personality disorders. One psychosocial treatment option for patients with personality disorders is the therapeutic community (TC). In 2000, the authors conducted a small qualitative study with a sample of psychiatrists which suggested that TCs were not well understood and that the status of evidence on efficacy might be partly responsible for low referral numbers. This article reviews the evidence for the efficacy and cost-effectiveness of TCs as a treatment for personality disorders and considers which types of disorders are amenable to TC treatment. We conclude that there is a strong case for more rigorous evaluation and that some of the difficulties anticipated in applying randomized clinical trial (RCT) methodology to the study of TCs could be overcome.     

An event-related fMRI study of exogenous orienting: supporting evidence for the cortical basis of inhibition of return?

This event-related fMRI experiment examined the neural substrates of exogenous visuospatial attention. Exogenous attention produces a biphasic response pattern denoted by facilitation at short cue-target intervals and inhibition of return (IOR) at longer intervals. Whereas the volitional orienting of attention has been well described in the literature, the neural systems that support exogenous facilitation and IOR in humans are relatively unknown. In direct comparisons to valid facilitation trials, valid IOR trials produced unique foci of activation in the right posterior parietal, superior temporal, middle temporal, middle occipital, anterior cingulate, and dorsal medial thalamic areas. Valid IOR trials also resulted in activation of motor exploratory and frontal areas previously associated with inhibition and oculomotor control. In contrast, invalid IOR compared to facilitation trials only activated anterior cortical structures. These results provide support for both attentional and oculomotor theories of IOR and suggest that IOR may be mediated by two networks. One network may mediate the inhibitory bias following an exogenous cue, whereas a separate network may be activated when a response must be made to stimuli that appear in inhibited locations of space.