scholarly journals Neural correlates of the contents of visual awareness in humans

2007 ◽  
Vol 362 (1481) ◽  
pp. 877-886 ◽  
Author(s):  
Geraint Rees
Keyword(s):  
Neural Activity ◽  
Brain Area ◽  
Visual Awareness ◽  
Sufficient Conditions ◽  
Neural Correlates ◽  
Neural Mechanisms ◽  
Great Promise ◽  
Visual Areas ◽  
Frontal Activity ◽  
Necessary And Sufficient

The immediacy and directness of our subjective visual experience belies the complexity of the neural mechanisms involved, which remain incompletely understood. This review focuses on how the subjective contents of human visual awareness are encoded in neural activity. Empirical evidence to date suggests that no single brain area is both necessary and sufficient for consciousness. Instead, necessary and sufficient conditions appear to involve both activation of a distributed representation of the visual scene in primary visual cortex and ventral visual areas, plus parietal and frontal activity. The key empirical focus is now on characterizing qualitative differences in the type of neural activity in these areas underlying conscious and unconscious processing. To this end, recent progress in developing novel approaches to accurately decoding the contents of consciousness from brief samples of neural activity show great promise.

scholarly journals Single units and conscious vision

1998 ◽  
Vol 353 (1377) ◽  
pp. 1801-1818 ◽  
Author(s):  
◽  
N. K. Logothetis
Keyword(s):  
Binocular Rivalry ◽  
Neural Activity ◽  
Visual Awareness ◽  
Physiological Data ◽  
Neural Basis ◽  
Binocular Fusion ◽  
Neural Representations ◽  
Multistable Perception ◽  
Visual Areas ◽  
Psychophysical Studies

Figures that can be seen in more than one way are invaluable tools for the study of the neural basis of visual awareness, because such stimuli permit the dissociation of the neural responses that underlie what we perceive at any given time from those forming the sensory representation of a visual pattern. To study the former type of responses, monkeys were subjected to binocular rivalry, and the response of neurons in a number of different visual areas was studied while the animals reported their alternating percepts by pulling levers. Perception–related modulations of neural activity were found to occur to different extents in different cortical visual areas. The cells that were affected by suppression were almost exclusively binocular, and their proportion was found to increase in the higher processing stages of the visual system. The strongest correlations between neural activity and perception were observed in the visual areas of the temporal lobe. A strikingly large number of neurons in the early visual areas remained active during the perceptual suppression of the stimulus, a finding suggesting that conscious visual perception might be mediated by only a subset of the cells exhibiting stimulus selective responses. These physiological findings, together with a number of recent psychophysical studies, offer a new explanation of the phenomenon of binocular rivalry. Indeed, rivalry has long been considered to be closely linked with binocular fusion and stereopsis, and the sequences of dominance and suppression have been viewed as the result of competition between the two monocular channels. The physiological data presented here are incompatible with this interpretation. Rather than reflecting interocular competition, the rivalry is most probably between the two different central neural representations generated by the dichoptically presented stimuli. The mechanisms of rivalry are probably the same as, or very similar to, those underlying multistable perception in general, and further physiological studies might reveal a much about the neural mechanisms of our perceptual organization.

scholarly journals Neural correlates of beauty retouching to enhance attractiveness of self-depictions in women

2020 ◽  
Author(s):  
Chisa Ota ◽  
Tamami Nakano
Keyword(s):  
Magnetic Resonance Imaging ◽  
Social Media ◽  
Neural Activity ◽  
Facial Attractiveness ◽  
Neural Correlates ◽  
Neural Mechanisms ◽  
Functional Magnetic Resonance ◽  
Resonance Imaging ◽  
Amygdala Activity ◽  
Increased Activity

AbstractBeauty filters, while often employed for retouching photos to appear more attractive on social media, when used in excess cause images to give a distorted impression. The neural mechanisms underlying this change in facial attractiveness according to beauty retouching level remain unknown. The present study used functional magnetic resonance imaging in women as they viewed photos of their own face or unknown faces that had been retouched at three levels: no, mild, and extreme. The activity in the nucleus accumbens (NA) exhibited a positive correlation with facial attractiveness, whereas amygdala activity showed a negative correlation with attractiveness. Even though the participants rated others’ faces as more attractive than their own, the NA showed increased activity only for their mildly retouched own face and the amygdala exhibited greater activation in the others’ faces condition than the own face condition. Moreover, amygdala activity was greater for extremely retouched faces than for unretouched or mildly retouched faces for both conditions. Frontotemporal and cortical midline areas showed greater activation for one’s own than others’ faces, but such self-related activation was absent when extremely retouched. These results suggest that neural activity dynamically switches between the NA and amygdala according to perceived attractiveness of one’s face.

scholarly journals A neural representation of invisibility: when stimulus-specific neural activity negatively correlates with conscious experience

2020 ◽  
Author(s):  
Matthew J Davidson ◽  
Will Mithen ◽  
Hinze Hogendoorn ◽  
Jeroen J.A. van Boxtel ◽  
Naotsugu Tsuchiya
Keyword(s):  
Neural Activity ◽  
Conscious Experience ◽  
Visual Awareness ◽  
Neural Correlates ◽  
Focus Of Attention ◽  
Neural Representation ◽  
Visually Evoked Potentials ◽  
Neural Responses ◽  
Visual Objects ◽  
Human Participants

AbstractAlthough visual awareness of an object typically increases neural responses, we identify a neural response that increases prior to perceptual disappearances, and that scales with the amount of invisibility reported during perceptual filling-in. These findings challenge long-held assumptions regarding the neural correlates of consciousness and entrained visually evoked potentials, by showing that the strength of stimulus-specific neural activity can encode the conscious absence of a stimulus.Significance StatementThe focus of attention and the contents of consciousness frequently overlap. Yet what happens if this common correlation is broken? To test this, we asked human participants to attend and report on the invisibility of four visual objects which seemed to disappear, yet actually remained on screen. We found that neural activity increased, rather than decreased, when targets became invisible. This coincided with measures of attention that also increased when stimuli disappeared. Together, our data support recent suggestions that attention and conscious perception are distinct and separable. In our experiment, neural measures more strongly follow attention.

scholarly journals Neural correlates of winning and losing fights in poison frog tadpoles

2020 ◽  
Author(s):  
Eva K Fischer ◽  
Harmony Alvarez ◽  
Katherine M Lagerstrom ◽  
Jordan E McKinney ◽  
Randi Petrillo ◽  
...  
Keyword(s):  
Neural Activity ◽  
Preoptic Area ◽  
Neural Correlates ◽  
Neural Mechanisms ◽  
Arginine Vasotocin ◽  
Water Volume ◽  
Neural Activation ◽  
Neural Basis ◽  
Poison Frog ◽  
Frog Tadpoles

ABSTRACTAggressive competition for resources among juveniles is documented in many species, but the neural mechanisms regulating this behavior in young animals are poorly understood. In poison frogs, increased parental care is associated with decreased water volume of tadpole pools, resource limitation, and aggression. Indeed, the tadpoles of many poison frog species will attack, kill, and cannibalize other tadpoles. We examined the neural basis of conspecific aggression in Dyeing poison frog (Dendrobates tinctorius) tadpoles by comparing individuals that won aggressive encounters, lost aggressive encounters, or did not engage in a fight. We first compared patterns of generalized neural activity using immunohistochemical detection of phosphorylated ribosomes (pS6) as a proxy for neural activation associated with behavior. We found increased neural activity in the medial pallium and preoptic area of loser tadpoles, suggesting the amphibian homologs of the mammalian hippocampus and preoptic area may facilitate loser-associated behaviors. Nonapeptides (arginine vasotocin and mesotocin) and dopamine have been linked to aggression in other vertebrates and are located in the preoptic area. We next examined neural activity specifically in nonapeptide- and tyrosine-hydroxylase-positive cells using double-label immunohistochemistry. We found increased neural activity specifically in the preoptic area nonapeptide neurons of winners, whereas we found no differences in activity of dopaminergic cells among behavioral groups. Our findings suggest the neural correlates of aggression in poison frog tadpoles are similar to neural mechanisms mediating aggression in adults and juveniles of other vertebrate taxa.

scholarly journals Neural Correlates of Metamemory: A Comparison of Feeling-of-Knowing and Retrospective Confidence Judgments

2009 ◽  
Vol 21 (9) ◽  
pp. 1751-1765 ◽  
Author(s):  
Elizabeth F. Chua ◽  
Daniel L. Schacter ◽  
Reisa A. Sperling
Keyword(s):  
Neural Activity ◽  
Visual Processing ◽  
Memory Retrieval ◽  
Medial Temporal Lobe ◽  
Neural Correlates ◽  
Neural Mechanisms ◽  
Multiple Forms ◽  
Functional Roles ◽  
Feeling Of Knowing ◽  
Metamemory Monitoring

Metamemory refers to knowledge and monitoring of one's own memory. Metamemory monitoring can be done prospectively with respect to subsequent memory retrieval or retrospectively with respect to previous memory retrieval. In this study, we used fMRI to compare neural activity during prospective feeling-of-knowing and retrospective confidence tasks in order to examine common and distinct mechanisms supporting multiple forms of metamemory monitoring. Both metamemory tasks, compared to non-metamemory tasks, were associated with greater activity in medial prefrontal, medial parietal, and lateral parietal regions, which have previously been implicated in internally directed cognition. Furthermore, compared to non-metamemory tasks, metamemory tasks were associated with less activity in occipital regions, and in lateral inferior frontal and dorsal medial prefrontal regions, which have previously shown involvement in visual processing and stimulus-oriented attention, respectively. Thus, neural activity related to metamemory is characterized by both a shift toward internally directed cognition and away from externally directed cognition. Several regions demonstrated differences in neural activity between feeling-of-knowing and confidence tasks, including fusiform, medial temporal lobe, and medial parietal regions; furthermore, these regions also showed interaction effects between task and the subjective metamemory rating, suggesting that they are sensitive to the information monitored in each particular task. These findings demonstrate both common and distinct neural mechanisms supporting metamemory processes and also serve to elucidate the functional roles of previously characterized brain networks.

scholarly journals Spatiotemporally distinct neural mechanisms underlie our reactions to and comparison between value-based options

2019 ◽  
Author(s):  
R. Frömer ◽  
A. Shenhav
Keyword(s):  
Neural Activity ◽  
Consumer Goods ◽  
Neural Correlates ◽  
Neural Mechanisms ◽  
Response Patterns ◽  
Related Activity

AbstractPrevious research suggests that people evaluate options in at least two ways: (1) appraising their overall value and (2) choosing between them. Here we test whether these processes are temporally dissociable, with appraisal-related processes tied to the time one’s options appear and choice-related processes tied to the time a decision is made. We recorded EEG while participants individually rated and subsequently made choices between consumer goods. As predicted, we found appraisal-related neural activity locked to the onset of the stimuli and choice-related activity locked to (and preceding) the response. Patterns of appraisal- and choice-related activity were further associated with distinct topographical profiles. Using a novel neural index of one’s certainty about a given item’s value, we also provide evidence that choices and choice-related activity were further modulated by this option-specific value certainty. Taken together, our results support the hypothesis that spatiotemporally distinct mechanisms underlie appraisal and choice, suggesting that commonly observed neural correlates of choice value may reflect either or both of these processes.

The extinction time of a general birth and death process with catastrophes

1986 ◽  
Vol 23 (04) ◽  
pp. 851-858 ◽  
Author(s):  
P. J. Brockwell
Keyword(s):  
Laplace Transform ◽  
Size Distribution ◽  
Sufficient Conditions ◽  
Necessary And Sufficient Conditions ◽  
Death Process ◽  
Extinction Time ◽  
Birth And Death Process ◽  
Different Types ◽  
The Laplace Transform ◽  
Necessary And Sufficient

The Laplace transform of the extinction time is determined for a general birth and death process with arbitrary catastrophe rate and catastrophe size distribution. It is assumed only that the birth rates satisfyλ0= 0,λj> 0 for eachj> 0, and. Necessary and sufficient conditions for certain extinction of the population are derived. The results are applied to the linear birth and death process (λj=jλ, µj=jμ) with catastrophes of several different types.

Budgeting in Socio-economic Development Strategies (Raising a Problem)

2008 ◽  
pp. 134-151
Author(s):  
A. Shastitko ◽  
M. Ovchinnikov
Keyword(s):  
Economic Policy ◽  
Economic Development ◽  
Social Change ◽  
Eastern Europe ◽  
Statistical Data ◽  
Sufficient Conditions ◽  
Transitional Period ◽  
Socio Economic Development ◽  
Necessary And Sufficient ◽  
Economic Development Strategies

The article proposes an approach to the analysis of social change and contributes to the clarification of concepts of economic policy. It deals in particular with the notion of "change of system". The author considers positive and normative aspects of the analysis of capitalist and socialist systems. The necessary and sufficient conditions for the system to be changed are introduced, their fulfillment is discussed drawing upon the historical and statistical data. The article describes both economic and political peculiarities of the transitional period in different countries, especially in Eastern Europe.

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