Thalamic and cortical mechanisms of anesthetic-induced unconsciousness

麻醉引起无意识的丘脑和皮质机制

• 批准号: 8990491
• 负责人: Matthew I Banks
• 金额: $ 28.91万
• 依托单位: UNIVERSITY OF WISCONSIN-MADISON
• 依托单位国家: 美国
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-02-15 至 2017-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8990491
• 关键词: Adverse effects; Anesthesia procedures; Anesthetics; Area; Auditory; Auditory area; Awareness; Biological Assay; Brain Stem; Cell Nucleus; Cells; Clinical; Code; Conscious; Cortical Column; Data; Development; Dexmedetomidine; Diagnostic; Dose; Electrodes; Electrophysiology (science); General anesthetic drugs; Health; Implant; Ipsilateral; Isoflurane; Link; Measures; Midbrain structure; Minimally Conscious States; Modality; Modeling; Molecular; Monitor; Operating Rooms; Output; Pathway interactions; Patient Care; Patients; Population; Process; Propofol; Public Health; Rattus; Recovery; Science; Sensory; Source; Stimulus; Surface; Synapses; Techniques; Testing; Thalamic structure; Unconscious State; Visual; Visual Cortex; auditory stimulus; awake; base; causal model; density; drug development; extrastriate visual cortex; hypnotic; insight; microstimulation; prevent; relating to nervous system; research study; response; segregation; sensory input; sensory stimulus; theories; tool; visual stimulus

DESCRIPTION (provided by applicant): Elucidating the mechanism by which anesthetics cause loss of consciousness (LOC) will benefit patient care and provide insight into the neural basis of consciousness. In this proposal, we will test two competing hypotheses, the thalamic switch hypothesis (TSH) and the information integration theory of consciousness (IITC). In the former, disruption of thalamo-cortical information transfer is thought critical for LOC. The latter proposes that anesthetics act across wide areas of cortex to reduce the repertoire of network states (information) and connectivity (integration). We postulate that propofol, isoflurane and dexmedetomidine, acting at diverse molecular loci, share a common cortical mechanism for producing LOC: degradation of stimulus representation and suppression of cortico-cortical connectivity at just-hypnotic doses (i.e. those just causing LOC), which prevent incorporation of sensory information into cortical hierarchical processing. We will test these competing hypotheses by recording unit activity and local field potentials (LFPs) in rats chronically implanted with multisite electrodes in auditory thalamus and auditory and visual cortex. A practical benefit to public health will be assays of consciousness based on population codes and cortical connectivity derived from cortical surface recordings, which are readily obtained in clinical settings. The absence of sensory awareness is a manifestation of LOC that reflects degraded information transfer between the periphery and high order cortex, but where and how this breakdown occurs is unclear. In the first Aim, we will focus on how much information responses of cells in auditory cortex carry about sensory stimuli, both at the single cell level an at the population level, and how this information changes upon loss and recovery of consciousness (LOC/ROC). By recording auditory responses in two thalamic areas, MGv and MGd, and their respective hierarchically connected cortical targets, A1 and PAF, we can determine whether anesthetics block information transfer from thalamus to cortex, as predicted by the TSH, or whether even in the face of maintained thalamic input cortical responses become impoverished upon LOC due to observed changes in local network activity caused by anesthetics, consistent with the IITC. In the second and third Aims, we will investigate connectivity along the ascending and descending thalamo-cortical pathway. Here we will record synaptic and spiking activity in entire cortical columns in response to microstimulation and auditory and visual sensory stimuli to determine if connectivity changes upon LOC/ROC at thalamo-cortical synapses, as predicted by the TSH, or at cortico-cortical synapses, consistent with the IITC. We will use the information from these experiments to aid in seeking electrophysiological correlates of the state transitions manifested in LOC/ROC, and we will derive clinically accessible measures of sensory awareness based on population coding and cortical connectivity using state of the art analysis and modeling techniques.

描述（申请人提供）：阐明麻醉药导致意识丧失（LOC）的机制将有利于患者护理，并为意识的神经基础提供见解。在这个提议中，我们将检验两个相互竞争的假说，丘脑开关假说（TSH）和意识的信息整合理论（IITC）。在前者中，丘脑-皮层信息传递的中断被认为是LOC的关键。后者