Psychology, Department of

Receive updates for this collection

Rhythms of Consciousness: Binocular Rivalry Reveals Large-Scale Oscillatory Network Dynamics Mediating Visual Perception

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2009-07-03
Abstract: 

Consciousness has been proposed to emerge from functionally integrated large-scale ensembles of gamma-synchronous neural populations that form and dissolve at a frequency in the theta band. We propose that discrete moments of perceptual experience are implemented by transient gamma-band synchronization of relevant cortical regions, and that disintegration and reintegration of these assemblies is time-locked to ongoing theta oscillations. In support of this hypothesis we provide evidence that (1) perceptual switching during binocular rivalry is time-locked to gamma-band synchronizations which recur at a theta rate, indicating that the onset of new conscious percepts coincides with the emergence of a new gamma-synchronous assembly that is locked to an ongoing theta rhythm; (2) localization of the generators of these gamma rhythms reveals recurrent prefrontal and parietal sources; (3) theta modulation of gamma-band synchronization is observed between and within the activated brain regions. These results suggest that ongoing theta-modulated-gamma mechanisms periodically reintegrate a large-scale prefrontal-parietal network critical for perceptual experience. Moreover, activation and network inclusion of inferior temporal cortex and motor cortex uniquely occurs on the cycle immediately preceding responses signaling perceptual switching. This suggests that the essential prefrontal-parietal oscillatory network is expanded to include additional cortical regions relevant to tasks and perceptions furnishing consciousness at that moment, in this case image processing and response initiation, and that these activations occur within a time frame consistent with the notion that conscious processes directly affect behaviour.

Document type: 
Article
File(s): 

Electrical Neuroimaging Reveals Timing of Attentional Control Activity in Human Brain

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2008-04
Abstract: 

Voluntarily shifting attention to a location of the visual field improves the perception of events that occur there. Regions of frontal cortex are thought to provide the top-down control signal that initiates a shift of attention, but because of the temporal limitations of functional brain imaging, the timing and sequence of attentional-control operations remain unknown. We used a new analytical technique (beamformer spatial filtering) to reconstruct the anatomical sources of low-frequency brain waves in humans associated with attentional control across time. Following a signal to shift attention, control activity was seen in parietal cortex 100–200 ms before activity was seen in frontal cortex. Parietal cortex was then reactivated prior to anticipatory biasing of activity in occipital cortex. The magnitudes of early parietal activations were strongly predictive of the degree of attentional improvement in perceptual performance. These results show that parietal cortex, not frontal cortex, provides the initial signals to shift attention and indicate that top-down attentional control is not purely top down.

Document type: 
Article
File(s): 

Standards of Evidence in Chronobiology: Critical Review of a Report that Restoration of Bmal1 Expression in the Dorsomedial Hypothalamus is Sufficient to Restore Circadian Food Anticipatory Rhythms in Bmal1-/- Mice

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2009
Abstract: 

Daily feeding schedules generate food anticipatory rhythms of behavior and physiology that exhibitcanonical properties of circadian clock control. The molecular mechanisms and location of foodentrainablecircadian oscillators hypothesized to control food anticipatory rhythms are unknown.In 2008, Fuller et al reported that food-entrainable circadian rhythms are absent in mice bearing anull mutation of the circadian clock gene Bmal1 and that these rhythms can be rescued by virallymediatedrestoration of Bmal1 expression in the dorsomedial nucleus of the hypothalamus (DMH)but not in the suprachiasmatic nucleus (site of the master light-entrainable circadian pacemaker).These results, taken together with controversial DMH lesion results published by the samelaboratory, appear to establish the DMH as the site of a Bmal1-dependent circadian mechanismnecessary and sufficient for food anticipatory rhythms. However, careful examination of themanuscript reveals numerous weaknesses in the evidence as presented. These problems aregrouped as follows and elaborated in detail: 1. data management issues (apparent misalignments ofplotted data), 2. failure of evidence to support the major conclusions, and 3. missing data andmethodological details. The Fuller et al results are therefore considered inconclusive, and fail toclarify the role of either the DMH or Bmal1 in the expression of food-entrainable circadian rhythmsin rodents.

Document type: 
Article
File(s): 

Food Anticipation in Bmal1-/- and AAV-Bmal1 Rescued Mice: A Reply to Fuller et al

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2009
Abstract: 

Evidence that circadian food-anticipatory activity and temperature rhythms are absent in Bmal1knockout mice and rescued by restoration of Bmal1 expression selectively in the dorsomedialhypothalamus was published in 2008 by Fuller et al and critiqued in 2009 by Mistlberger et al. Fulleret al have responded to the critique with new information. Here we update our critique in the lightof this new information. We also identify and correct factual and conceptual errors in the Fuller etal response. We conclude that the original results of Fuller et al remain inconclusive and fail toclarify the role of Bmal1 or the dorsomedial hypothalamus in the generation of food-entrainablerhythms in mice.

Document type: 
Article

Cognition in Anxious Children with Attention Deficit Hyperactivity Disorder: A Comparison with Clinical and Normal Children

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2007
Abstract: 

Background: Cognition in children with anxiety disorders (ANX) and comorbid Attention DeficitDisorder (ADHD) has received little attention, potentially impacting clinical and academicinterventions in this highly disabled group. This study examined several cognitive features relativeto children with either pure condition and to normal controls.Methods: One hundred and eight children ages 8–12 and parents were diagnosed by semistructuredparent interview and teacher report as having: ANX (any anxiety disorder except OCDor PTSD; n = 52), ADHD (n = 21), or ANX + ADHD (n = 35). All completed measures of academicability, emotional perception, and working memory. Clinical subjects were compared to 35 normalcontrols from local schools.Results: Groups did not differ significantly on age, gender, or estimated IQ. On analyses ofvariance, groups differed on academic functioning (Wide Range Achievement Test, p < .001),perception of emotion (auditory perception of anger, p < .05), and working memory (backwardsdigits, p < .01; backwards finger windows, p < .05; Chipasat task, p < .001). ANX + ADHD andchildren with ADHD did poorly relative to controls on all differentiating measures except auditoryperception of anger, where ANX + ADHD showed less sensitivity than children with ANX or withADHD.Conclusion: Though requiring replication, findings suggest that ANX + ADHD relates to greatercognitive and academic vulnerability than ANX, but may relate to reduced perception of anger.

Document type: 
Article