Layer I of primary sensory neocortex: where top-down converges upon bottom-up

Cauller, Lawrence J.

doi:10.1016/0166-4328(95)00032-1

Cited by 189 publications

(149 citation statements)

References 33 publications

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“…Schroeder has argued that multisensory convergence at early stages indicates a high-order function at lowlevel sensory cortices, which is compatible with reverse hierarchy theory (Cauller, 1995;Hochstein & Ahissar, 2002;Schroeder et al, 2003). The auditory system is organized in parallel streams.…”

Section: Feedback Projections and Multisensory Integrationmentioning

confidence: 73%

Long-distance feedback projections to area V1: Implications for multisensory integration, spatial awareness, and visual consciousness

Clavagnier

Falchier

Kennedy

2004

Cognitive, Affective, & Behavioral Neuroscience

225

149

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Section: Feedback Projections and Multisensory Integrationmentioning

confidence: 73%

Long-distance feedback projections to area V1: Implications for multisensory integration, spatial awareness, and visual consciousness

Clavagnier

Falchier

Kennedy

2004

Cognitive, Affective, & Behavioral Neuroscience

225

149

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“…Importantly, there is substantial evidence to suggest that top-down processes not only play an important role in sensory processing in general but also are crucial for conscious perception, in particular [75][76][77][78][79][80][81][82] (see also the review articles by Pollen, 83 Lamme and Roelfsema, 84 Bullier, 85 Hochstein and Ahissar, 86 and Meyer 87 ). For example, when subjects perceive apparent motion (as is the case when two dots in different locations are seen in rapid alteration, creating the impression that a single dot is moving from one location to the other), there is V1 activity along the apparent motion trace (where there is no actual visual stimulus), and this activity is induced by top-down signals.…”

Section: Top-down Signals and Conscious Perception: What We Already Knowmentioning

confidence: 99%

“…77 Similar findings exist for the somatosensory modality: the subjective intensity of tactile stimuli is reflected in top-down signals that reach layer 1 of the primary somatosensory cortex from higher-level areas rather than in the thalamocortical signals that initially arrive in layer 4. 75,76 As an additional observation, which applies equally to the visual, auditory, and somatosensory modalities, there is an interdependency of the latency of sensory cortex responses and their correlation with conscious experience: although early activity in the sensory areas appears to be strictly stimulus bound, later activity, which reflects top-down signals from higher-order cortices, is correlated more closely with the subject's conscious percept. 24,75,76,79,89,90 Thus, several lines of evidence from neuroanatomy, neurophysiology, and functional neuroimaging suggest that top-down signaling fulfills an indispensable function in conscious perception.…”

Section: Top-down Signals and Conscious Perception: What We Already Knowmentioning

confidence: 99%

“…75,76 As an additional observation, which applies equally to the visual, auditory, and somatosensory modalities, there is an interdependency of the latency of sensory cortex responses and their correlation with conscious experience: although early activity in the sensory areas appears to be strictly stimulus bound, later activity, which reflects top-down signals from higher-order cortices, is correlated more closely with the subject's conscious percept. 24,75,76,79,89,90 Thus, several lines of evidence from neuroanatomy, neurophysiology, and functional neuroimaging suggest that top-down signaling fulfills an indispensable function in conscious perception. Accordingly, if general anesthetics interrupt top-down processing, as suggested by the studies reviewed at the outset of the article, this would be one potential mechanism by virtue of which they may suspend consciousness.…”

Section: Top-down Signals and Conscious Perception: What We Already Knowmentioning

confidence: 99%

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The Role of Dendritic Signaling in the Anesthetic Suppression of Consciousness

Meyer

2015

Anesthesiology

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Despite considerable progress in the identification of the molecular targets of general anesthetics, it remains unclear how these drugs affect the brain at the systems level to suppress consciousness. According to recent proposals, anesthetics may achieve this feat by interfering with corticocortical topdown processes, that is, by interrupting information flow from association to early sensory cortices. Such a view entails two immediate questions. First, at which anatomical site, and by virtue of which physiological mechanism, do anesthetics interfere with top-down signals? Second, why does a breakdown of top-down signaling cause unconsciousness? While an answer to the first question can be gleaned from emerging neurophysiological evidence on dendritic signaling in cortical pyramidal neurons, a response to the second is offered by increasingly popular theoretical frameworks that place the element of prediction at the heart of conscious perception. Science magazine posed this question in a special section titled "What don't we know?," dedicated to the greatest challenges of contemporary science. 1 "Scientists are chipping away at the drugs' effects on individual neurons," the article reads, "but understanding how they render us unconscious will be a tougher nut to crack." This prediction proved correct: a decade later, we have expanded considerably our knowledge of the molecular targets of general anesthetics, but it remains enigmatic how these drugs affect the brain at the systems level. Why does the potentiation of γ-aminobutyric acid (GABA) receptors caused by propofol or desflurane cause unconsciousness? How are the brain's computational processes affected by this and other molecular mechanisms of anesthetics, so that patients undergoing surgery cease to experience their surrounds in terms of sight, sound, and touch? Anesthesiologists and cognitive neuroscientists alike have been captivated by these questions and have proposed a number of models in an attempt to answer them, such as Flohr's "information processing theory of anesthesia," 2 Alkire's "thalamic consciousness switch hypothesis," 3-6 Mashour's "cognitive unbinding paradigm," 7,8 John and Prichep's "anesthetic cascade," 9 or Hudetz's "forgotten present." 10,11 We shall return to some of these frameworks in a later section of the article.One recent development is particularly intriguing. Given that the most striking feature of general anesthesia is an interruption of the patient's ability to perceive the environment, it would appear intuitive for anesthetics to interfere primarily with bottom-up information flow along the sensory pathways, that is, with the signals that carry perceptual information from the thalamus to the primary sensory cortices and on to unimodal and multimodal association cortices. However, the very opposite appears to be the case. Several recent studies-carried out in both humans and animals, and using a variety of different anesthetic agents-have investigated differences in directional corticocortical connectivity bet...

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“…It also integrates higher mental functions, general movement, visceral functions, and behavioral reactions. (Brodal, 1977;Cauller, 1995). It is constituted of up to six horizontal layers, each of which has a different composition in terms of neurons and connectivity.…”

Section: Introductionmentioning

confidence: 99%

Effects of Aluminium Chloride Exposure on the Histology of the Cerebral Cortex of Adult Wistar Rats

Buraimoh

Ojo

Hambolu

et al. 2012

JBLS

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AbstractsAluminium (Al) is presents in many manufactured foods, medicines and is also added to drinking water for purification purposes. Human exposure to Al has been increasing over the last decades. Al exposure and neurological impairments demonstrate mixed findings. The cerebral cortex is a sheet of neural tissue that is outer-most to the cerebrum of the mammalian brain and it plays a key role in memory, attention, perceptual awareness, thought, language, and consciousness.The objectives of this study was to investigate the possible effects that aluminium Chloride could have on the histology of cerebral cortex. Total of twenty adult wistar rats were used for this experiment. The wistar rats were divided into five groups; group I was the control, group II received 475mg/Kg, group III received 950mg/kg, group IV received 1,425mg/kg and group V received 1,900mg/kg via oral intubation for a duration of Eight weeks. The wistar rats were humanly sacrificed and the brain was removed and immediately fixed in bouin fluid. The histological observations of the aluminium treated groups revealed extensive neuronal vacuolation and necrosis (neuro-degeneration) of the cerebral cortex of wistar rats.Based on our observations, we therefore conclude that Aluminium chloride exposure has neurodegenerative effects on the histology of cerebral cortex of adult wistar rats especially at higher dose. Therefore, caution should be taken in its usage.

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Layer I of primary sensory neocortex: where top-down converges upon bottom-up

Cited by 189 publications

References 33 publications

Long-distance feedback projections to area V1: Implications for multisensory integration, spatial awareness, and visual consciousness

Long-distance feedback projections to area V1: Implications for multisensory integration, spatial awareness, and visual consciousness

The Role of Dendritic Signaling in the Anesthetic Suppression of Consciousness

Effects of Aluminium Chloride Exposure on the Histology of the Cerebral Cortex of Adult Wistar Rats

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