Flexible cortical gamma-band correlations suggest neural principles of visual processing

We summarize recent studies of our group from the primary visual cortex V1 of behaving monkeys referring to the hypothesis of spatial feature binding by γ-synchronization (30-90 Hz). In agreement with this hypothesis the data demonstrates decoupling of γ-activities among neural groups representing figure and ground. As γ-synchronization in V1 is restricted to cortical ranges of few millimeters, feature binding may equivalently be restricted in visual space. Closer inspection shows that the restriction in synchrony is due to far-reaching travelling γ-waves with changing phase coupling. Based on this observation we extend the initial binding-by-synchronization hypothesis and suggest object continuity to be coded by phase continuity. It is further argued that the spatial phase changes of the V1 γ-waves in general will also limit lateral phase coupling to higher levels of processing. Instead of phase-locked γ-coupling, corticocortical cooperation among γ-processes may be mediated by mutual amplitude modulations that are more reliable than phase synchrony over larger distances. The relevance of this concept of corticocortical binding is demonstrated with subdural recordings from human subjects performing cognitive tasks. The experimental results are discussed on the basis of network models with spiking neurons.     

Compliance and Problem-Solving Competence in Girls and Boys

The problem-solving abilities of 4- and 5-year old children (N = 208) were assessed to test the hypothesis that high levels of compliance are negatively related to problem solving. Problem-solving competence was examined with a task-specific measure and a standardized measure of general problem-solving performance. Low compliant children performed better on both measures. The role of compliance in the cognitive development of girls and boys is discussed.     

Caregiver models of self and others, coping, and depression: predictors of depression in children with chronic pain.

In a sample of 59 chronically ill pediatric patients and their maternal caregivers, both child-reported pain and caregiver-reported depression predicted child-reported depression. Results further suggested that the association between pain and depression in children is ameliorated by caregiver coping strategies and that how caregivers cope is a function of their attachment-related representations of the self and others. Caregivers with a negative model of the self were more depressed. and those with a negative model of others were more prone to use avoidant coping strategies, and, in turn, to be more depressed. However, the extent to which caregivers with negative models of self used more avoidant and less approach coping appeared to depend on whether they perceived that others were likely to respond to their needs.     

Networks of neurons, networks of genes: an integrated view of memory consolidation

Investigations into the mechanisms of memory formation have abided by the central tenet of the consolidation theory-that memory formation occurs in stages which differ in their requirement for protein synthesis. The current most widely accepted hypothesis posits that new memories are encoded as neural activity-induced changes in synaptic efficacy, and stabilization of these changes requires de novo protein synthesis. However, the basic assumptions of this view have been challenged by concerns regarding the specificity of the effects of the protein synthesis inhibitors used to support the claim. Studies on immediate-early genes (IEGs), in particular Arc, provide a distinct and independent perspective on the issue of the requirement of new protein synthesis in synaptic plasticity and memory consolidation. The IEG Arc and its protein are dynamically induced in response to neuronal activity, and are directly involved in synaptic plasticity and memory consolidation. Although we provide extensive data on Arc's properties to address the requirement of genomic and proteomic responses in memory formation, Arc is merely one element in a network of genes that interact in a coordinated fashion to serve memory consolidation. From gene expression and other studies, we propose the view that the stabilization of a memory trace is a continuous and ongoing process, which does not have a discrete endpoint and cannot be reduced to a single deterministic "molecular cascade". Rather, memory traces are maintained within metastable networks, which must integrate and update past traces with new ones. Such an updating process may well recruit and use many of the plasticity mechanisms necessary for the initial encoding of memory.     

Psychotic manifestations in a patient with mental retardation and a 6.2 megabase deletion at the distal short arm of chromosome 12

Genetic factors are known to contribute to the development of schizophrenia and related psychoses. Cytogenetic abnormalities have been occasionally found in patients with psychotic disorders and, thus, have helped identify candidate gene contributors for these conditions. The individual described here first presented with mental retardation and anxiety disorder in his mid-childhood. In his early 20s, the patient started exhibiting various psychotic manifestations, including delusions and hallucinations. His psychotic symptoms were difficult to control with psychotropic medications. The family history was negative for psychiatric disorders. This patient was found to have a 6.2 megabase deletion of the terminal portion of the short arm of chromosome 12 that was characterized using fluorescence in situ hybridization and microarray comparative genomic hybridization analysis. The maternal chromosomes were normal, but the paternal chromosomes could not be tested. To-date such a chromosomal abnormality has not been described in association with schizophrenia/psychosis. This case suggests that psychosis-associated gene(s) may be located in the terminal region of the short arm of chromosome 12.