While dual task load during encoding lead to reductions in the frequency of the subjective experience of conscious recollection and reductions in overall context memory, joint context memory was not affected. Furthermore, the relation of higher overall context memory for consciously recollected items than for familiar items was preserved even under dual task load.
Figure 1. Task refinements and No-report paradigms To study the neural basis of mental states, such as conscious contents, behavioral reports, such as button presses or eye movements, seem necessary. Figure 2. Lesion and inactivation studies Human patients and monkeys with lesions in primary visual cortex V1 are blind at the corresponding visual field location; therefore, the role of V1 as a prerequisite for visual consciousness seems unequivocal Tong, ; Maier et al.
Figure 3. Are the neural correlates of consciousness mainly in the front or in the back of the cerebral cortex? Measuring brain complexity to detect and promote the recovery of consciousness. The conscious rodent brain: ensemble activity and long-range correlation patterns Animal models provide a unique window to probe the neuron-level mechanisms of many cognitive processes, including consciousness. Figure 4. The authors declare no competing financial interests. Correspondence should be addressed to Dr. Elife 4 : e Science : — J Neurosci 32 : — Neurosci Biobehav Rev 36 : — Brain : — Barton JJ Disorders of higher visual processing.
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Attention and consciousness - Scholarpedia
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Conscious Cogn 18 : — Pennartz CM The brain's representational power: on consciousness and the integration of modalities. J Cogn Neurosci 29 : — Surprisingly, seemingly complex peripheral tasks can be done equally well under either single or dual-task condition Li et al. The dual-task paradigm quantifies what type of stimulus attributes can be signaled and possibly consciously perceived in the near absence of spatial attention VanRullen et al. Most importantly, the dual-task paradigm can be combined with a multitude of visual illusions that render stimuli invisible, allowing the independent manipulation of top-down attention and consciousness Figure 3 , although such a full factorial analysis for many popular experiments awaits future work Opposite Effects.
The consciousness circuit - an approach to the hard problem.
The inference of attentional requirements from dual-task performance demands caution. High proficiency in such tasks is only achieved after extensive training of many hours.
Finally, there is a class of neurological conditions as well as visual illusions in normal subjects where stimuli become invisible because of impairments in the mechanisms of top-down or bottom-up attention. Hemineglect and extinction Driver and Mattingley, , attentional blink Raymond et al. Although some attributes of the visual input need attentional amplification to rise to the level of consciousness, other aspects, such as the gist of the scene and its emotional content, are quite resistant to such attentional manipulations Mack and Rock, ; Anderson and Phelps, Exogenous cues are image-immanent features that transiently attract attention or eye gaze, independent of any particular task.
Thus, if an object attribute for example, flicker, motion, color, orientation, depth, or texture differs significantly from its value in some neighborhood, the object will be salient. Such algorithms account for a significant fraction of fixation eye movements Parkhurst et al.
Candidates for such a map in the primate brain include the initial responses of neurons in the frontal eye field FEF and the lateral intraparietal sulcus LIP Constantinidis and Steinmetz, ; Thompson and Bichot, Visual input can be classified very rapidly. As famously demonstrated by Thorpe and colleagues Thorpe et al. At this speed, it is no surprise that subjects often respond without having consciously seen the image VanRullen et al. Dual-task and dual-presentation paradigms support the idea that such discriminations can occur in the near-absence of focal, spatial attention Li et al.
Orthogonal Reality: Rotating in Consciousness
Animal experiments could substantiate this assertion. Imagine that all the cortico-cortical pathways from prefrontal cortex back to higher level visual cortex and from there on even further back to primary and secondary visual cortices could be transiently knocked out using a molecular silencing tool without compromising feed-forward processing. That is, for a couple of hours, the brain of the monkey would only support feed-forward pathways. It is quite likely that such an animal could still carry out a previously learned simple discrimination task with the same level of performance as prior to the intervention upper left quadrant in Table 1 Attention and Consciousness , without any top-down attention since prefrontal cortex would have no means to modulate the processes in the visual brain , and possibly without conscious perception although this latter would be difficult to demonstrate in an animal preparation.
In lateral masking visual crowding , the orientation of a peripherally-presented grating is hidden from conscious sight but remains sufficiently potent to induce an orientation-dependent aftereffect He et al. In this case, the orientation of the grating is not consciously accessible to the subject yet something is still seen at that location that is, in this case only some attributes of the object are invisible. Montaser-Kouhsari and Rajimehr showed that an aftereffect induced by an invisible illusory contour required focal attention to the aftereffect-inducing object, even though the attribute of that object at the center of attention was invisible.
Naccache and colleagues Naccache et al. In both cases, spatial or temporal attentional selection was necessary to obtain the aftereffect or priming even though the relevant attribute orientation, letter identity was invisible. Interestingly, in heterosexuals, these effects were only apparent for nudes of the opposite sex see also McCormick, ; Rajimehr, ; Sumner et al.
https://writypunizex.tk Note that by themselves i. Likewise, the blindsight patient GY has the usual reaction-time advantages for the detection of targets in his blind visual field when attentionally cued, even when the cues are located in his blind field and are therefore invisible to him Kentridge et al. Feature-based attention can spread to invisible stimuli Melcher et al. Indeed, when searching for an object in a cluttered scene e.
They varied the load of the central task in a dual-task design How to manipulate attention. The hemodynamic blood-oxygen-level-dependent contrast BOLD response to the invisible objects in primary visual cortex, V1, was stronger when the central task was easy, that is, when spatial attention was available for processing the invisible, peripheral stimulus than when the central task was hard and more attentional resources were drawn to it. In other words, available attentional capacity modulated the fMRI response to an invisible stimulus. An even more paradoxical effect - that invisible stimuli can be more distracting than visible ones — was discovered by Tsushima and colleagues Tsushima et al.
In this study, subjects had to detect foveally-placed targets in a stream of characters — a rapid serial visual presentation RSVP task - surrounded by an annulus of moving dots. Using the identical retinal layout, the subject either performs the central task, or the peripheral task, or both simultaneously Sperling and Dosher, ; Braun and Sagi, ; Braun and Julesz, With focal attention busy at the center, the subject can still distinguish a natural scene containing an animal or a vehicle from one that does not include an animal or a vehicle while being unable to distinguish a red-green bisected disk from a green-red one Li et al.
Likewise, subjects can tell male from female faces or even distinguish a famous from a non-famous face Reddy et al.
This is quite remarkable. Thus, although we cannot be sure that observers do not deploy some limited amount of top-down attention in these dual-task experiments that require training and concentration that is, high arousal , it remains true that subjects can perform certain discriminations but not others in the near-absence of top-down attention.
And they are not guessing. Can perception be studied in the complete absence of attention? This seems possible if, in the above-mentioned dual-task paradigm, subjects must perform a very demanding central task without needing to monitor the periphery. Such an experiment has been conducted to investigate the effects of attention on bistable perception Pastukhov and Braun, A fundamental question in the perception of ambiguous figures is why they switch spontaneously despite constant retinal input.
One influential theory posits that top-down attention triggers perceptual transitions James, To test this, Pastukhov and Braun Pastukhov and Braun, examined whether unattended and unreported bistable motion stimuli continued to switch. Consistent with other studies Paffen et al. In other words, top-down attention is not necessary for switches in the content of visual consciousness. Similar dual-task experiments can likewise be applied as a strict test for the necessity of top-down attention in learning, memory , adaptation, and other cognitive functions.
Attention and its neuronal correlate can be understood in the context of selection and biased competition Desimone and Duncan, : attention acts as a winner-take-all, enhancing one coalition of neurons representing the attended object at the expenses of others non-attended stimuli Lee et al.