Dynamic causal communication channels between neocortical areas

Processing of sensory information depends on the interactions between hierarchically connected neocortical regions, but it remains unclear how the activity in one area causally influences the activity dynamics in another and how rapidly such interactions change with time. Here, we show that the communication between the primary visual cortex (V1) and high-order visual area LM is context-dependent and surprisingly dynamic over time. By momentarily silencing one area while recording activity in the other, we find that both areas reliably affected changing subpopulations of target neurons within one hundred milliseconds while mice observed a visual stimulus. The influence of LM feedback on V1 responses became even more dynamic when the visual stimuli predicted a reward, causing fast changes in the geometry of V1 population activity and affecting stimulus coding in a context-dependent manner. Therefore, the functional interactions between cortical areas are not static but unfold through rapidly shifting communication subspaces whose dynamics depend on context when processing sensory information

A causal investigation of cortical communication

Distributed regions in the brain continuously interact - forming dynamic pathways of information flow which underlie the diversity of behaviour. Understanding how areas in the brain communicate is contingent on understanding the principles by which neuronal activity in one area causally influences activity in another. Achieving this goal has been challenging, due to the ambiguities arising from inferring cause-effect interactions from statistical relations of neuronal activity. Therefore, it is still unclear how cortical communication causally affects ongoing population activity patterns and if these inter-areal interactions can change over behaviourally relevant timescales and in different behavioural states. Here I introduce a causal approach to measure feedforward and feedback communication between primary and secondary visual cortex in mice performing a visual discrimination task. I assessed the instantaneous effect of optogenetically silencing one area on its target’s population activity and found the effect one cortical area had on another was surprisingly variable over time. Both feedforward and feedback pathways reliably affected different subpopulations of target neurons at different moments during processing of a visual stimulus, resulting in dynamically changing communication dimensions between the two cortical areas. The influence of feedback on V1 became even more dynamic when visual stimuli were behaviourally relevant and associated with a reward, impacting different subsets of V1 neurons within tens of milliseconds. Consequently, the patterns of correlated variability in V1 population activity - important for stimulus coding - dynamically restructured on rapid time-scales in a context-dependent manner. Thus, while cortical areas are connected by static anatomical pathways, they interact through highly flexible communication channels while evaluating sensory information

The Role of Nodes Distribution in Extending the Lifetime of Wireless Sensor Networks

One of the most important issues in sensor networks is prolonging the network lifetime. In this paper, we demonstrate that given a constant number of nodes, how distribution of nodes affects the lifetime. For this purpose, we first show that in a network with cluster-based routing protocol, nodes do not have equal importance, and their importance depends on their location, and we determine the most critical regions. We prove that the uniform distribution of nodes is not a good distribution. Finally, we propose a solution for the best distribution that concentrates the population of nodes on critical areas. Simulation results of our proposed distribution show a remarkable increase in network lifetime

Cerebral venous thrombosis in a child with inflammatory bowel disease: case report

Abstract  inflammatory bowel disease (IBD) has both intestinal and extra intestinal manifestations. Inflammatory bowel disease (IBD) is a known risk factor for cerebral venous thrombosis (CVT) event in adult and children. The precise mechanism of thrombotic event is not known in patient with IBD. We report a case of ulcerative colitis with CVT during admission for acute relapse. 12 years old boy known case of ulcerative colitis since 12 months ago admitted in children hospital because of bloody diarrhea, recurrent colicky abdominal pain. At the third day of admission patient had severe headache. Level of consciousness has decreased gradually during 12 hours. Child has been aphasic later. One episode of tonic clonic seizure has happened 18 hours after the onset of headache. Neurologic examination showed right hemiparesis. Physical examinations including blood pressure and fundoscopy were unremarkable in last admission. Brain CT shows intraparanchymal hemorrhage in left temporal lobe with asymmetric increased density in left lateral sinus.  The results of MRI has shown abnormal hyperintense signal in left lateral sinus in T1WI and T2WI that is compatible with thrombosis (loss of signal) in MRV. LMW heparin was administered according to consultation with hematologist and continued post discharge. Child condition has improved slowly and neurologic evaluation was normal after 3months. Cerebrovascular events, such as cerebral venous thrombosis (CVT) or cerebral arterial infarction (CAI), are rare extraintestinal manifestations of PIBD but probably the most common forms of thromboembolism in children. Probably, treatment of CVT with anticoagulants is the best way of management. A comprehensive study is essential to understand the choice, efficacy, duration, and primary and secondary prophylaxis protocol with anticoagulants