Consciousness and Cognition 21 (2012) 711–712

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Consciousness and Cognition

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Many times over: A brief reply to Lee and Klincewicz q

Dan LloydDepartment of Philosophy and Program in Neuroscience, Trinity College, Hartford, CT 06106, USA

Areas of the brain comprising the ‘‘Default Mode Network’’ encode (among other information) elapsed duration of restingperiods between tasks during an fMRI experiment: this is the empirical finding of the target article. The temporal encoding isquite specific and robust across subjects (see Fig. 1 in the target article). This result would add to the roster of functions pro-posed for the DMN; like other DM functions, timekeeping seems to engage independently of the tasks probed by the exper-iment. DMN time monitoring thus seems to be spontaneous and continual. Although the target article mentions this onlybriefly, it is worth noting that the DMN is not active exclusively during off-task periods. Rather, the DMN is only somewhatmore active during resting periods – in the subjects analyzed here around 60% of DMN activity occurred during rest periods,but this proportion is sufficient to establish a significant correlation between DMN activity and ‘‘rest.’’

Supposing that these empirical observations are generally correct, what are their implications for the scientific explana-tion of human consciousness? Is DMN activity the ‘‘neural correlate’’ of the conscious awareness of time? In their very usefulcommentaries, Geoffrey Lee and Michal Klincewicz both question the stretch from brain activity to conscious contents. Thisis a general problem in consciousness science, of course, and cognitive neuroscience and philosophy approach it somewhatdifferently. But from both the scientist’s and the philosopher’s standpoint, there is work to be done, beginning with the phe-nomenology of time.

I join with Husserl and his tradition in regarding temporal awareness as a structural feature of consciousness. But what ismeant by ‘‘structural’’? For some aspect of experience u to be a structural component of an experience of type A (exp-A)implies two interdependent necessary conditions. First, u must be present in every instance of experiences of type A. Second,u must be conceptually necessary for an experience to be of type A. That is, without u, exp-A would be an experience of adifferent type. Although the second condition implies the first, they are distinct, and in my opinion, James and Husserlequivocate between them in their analyses. This is understandable as the second condition is contentious in application.For example, objects of perception are transcendent, overflowing their immediately sensed contents, according to thephenomenological tradition. According to Husserl, perceived objects (physical objects as they appear in perception) alwayshave ‘‘horizons,’’ edges beyond which there are parts unseen. This is not a logical condition for being an object, but rather is acondition for an experience to be of an object. Take away the horizon (and with it the unseen transcendencies), and the expe-rience must be recategorized, as (for example) an after-image, or a fantasy image, rather than the perception of an object.When structural dimensions of an experience are noticed and attended to, they are part of the explicit contents of conscious-ness. But often they seem to be unnoticed. However, even then structural features are among the contents of consciousness,since they are constitutive of aspects of an experience whose type is a content of consciousness. For example, when we diveto catch a frisbee, we see it as an object with horizons that constitute its presence in space as a real existent. Without itsstructural features, the perceptual blob would be of an indefinite type, neither real nor imaginary.

Husserl and his followers regard temporality as a structural component of all experiences. Certainly the first structuralrequirement can be argued through numerous examples of our sensitivity to durations, intervals, the apparent passage oftime, and the like. Notably, temporal dimensions of experience ‘‘pop out’’ when the expected or desired timeline is violatedfor any object, event, or process. The stricter second condition is tougher to establish in this case, since temporality is pur-ported to be constitutive of all objects of consciousness. Arguably, change, motion, and continuity (and their absences) areinherent in all intentional objects. Likewise, recognizing novelty and repetition, sameness and variation, seems to be consti-

1053-8100/$ - see front matter � 2011 Elsevier Inc. All rights reserved.doi:10.1016/j.concog.2011.08.009

q Reply to ommentary on Klincewicz, M. (2012). Neural correlates of temporality? Consciousness and Cognition, 21, 704-706; Lee, G. (2012). Commentaryon Dan Lloyd: ‘‘Neural correlates of Temporality’’. Consciousness and Cognition, 21, 707-710. This article is part of a special issue of this journal on Standingon the Verge: Lessons and Limits from the Empirical study of Consciousness.

E-mail address: Dan.Lloyd@trincoll.edu

712 D. Lloyd / Consciousness and Cognition 21 (2012) 711–712

tutive of all experiences. All of these aspects of experiences depend on comparing experiences occurring at different times,and so all presuppose some form of temporality. A mental state that carried no contextual information about previous orsubsequent mental states would be undifferentiated in a way that seems alien to human consciousness. More generally, withevery experience comes an awareness of duration and the passage of time, which can be readily probed at scales from frac-tions of seconds to years. That is to say, a state lacking these time-dependent qualities would not be recognizably conscious(though it might nonetheless carry complex information about current environmental conditions).

This commentary is not the place to develop this line of thinking. From a scientific perspective, however, the distinctionbetween the first condition and the second may not be so important. Cognitive neuroscience seeks explanations for empiricalgeneralizations about human consciousness, regardless of whether these generalizations are contingent or necessary. If tem-porality is indeed a ubiquitous aspect of human experience (as seems to be the case), then its neural correlate will be a con-tinuous presence in conscious subjects. The neural correlate of temporality will therefore be detectable in various settings,not just those where timing is explicitly addressed. Indeed, to detect a structural feature of consciousness we need to look atexperiences where the target feature is not explicitly demanded by the conditions of an experiment. In the present case, theonsets and offsets of rest and task periods were assumed to be salient events for both retention and protention, and couldserve as anchors in the subjective time line for subjects. Although the target paper argues that temporality is an essentialstructural feature of experience, it is sufficient for the present to argue that this particular experimental condition, the alter-nation of 24-s blocks of demanding tasks and immobilized ‘‘rest,’’ would provoke explicit anticipation and retention. I agreewith the commentators that it would be desirable to have subject reports, but it is not clear what these reports would add.Would we expect any healthy subject to deny that time seems to be passing? Would any subject fail to notice if the durationof a task or rest block suddenly doubled or halved?

Assuming that the blood-oxygen-level-dependent response detected by fMRI is generated by neural activity, and in lightof the discussion above, how plausible is it to link the observed temporally-inflected neural correlate with the contents ofconsciousness in this experiment? Here also the philosopher and the scientist inhabit different epistemic worlds. Philosoph-ically, it is conceptually possible for any neural state to be a zombie brain state rather than a bearer of conscious content.Scientifically, however, it is amply warranted to suppose that at least some and possibly many brain states really do embodythe contents of consciousness. What, then, about the Default Mode Network, herein also named the Dynamic Temporal Net-work? The DMN comprises components that have been widely associated with paradigms of reflective awareness, prompt-ing several researchers to conjecture that the DMN correlates with the Jamesian stream of consciousness – as discussed inthe target article. If I am right that subjects in this experiment experience passing time, and in particular maintain a struc-tural awareness of elapsed time during particular phases of the experiment, then this temporal awareness enjoys the sameepistemic warrants as other correlations between the default mode and conscious mentation. Furthermore, temporal infor-mation rests on the dynamic interaction of all the DMN regions, with different intervals encoded by differing distributed pat-terns of activation in the DMN. These encoded intervals are anchored by the change from task to rest. The objects of theseevolving DM states are the onsets/offsets of tasks and rests, indexed by their temporal distance from the present. These on-sets and offset are surely part of the contents of consciousness, and their perception in a specific temporal landscape is anal-ogous to perception in space.

Ultimately, an adequate theory of consciousness will be satisfying to both the philosopher and the scientist. Researchersin consciousness science wear both hats, and I share their optimistic hope that as neurophenomenology expands its breadthand depth, the explanatory gap between consciousness and the brain will narrow. Perhaps it will never close, but thenmaybe we are just dreaming.