Welcome to the world of consciousness. It isboth thrilling and mysterious. It can amuse and itcan cause serious intellectual debate. It isfundamental to our definition of what makes ushuman and to our patronizing opinion of thecognitive and emotional capabilities of otherspecies. And it raises questions, many questions.There are at least two main questions that thoseentering the world of consciousness studies mustask: Can we define consciousness clearly? Whichbiological substrate does consciousness emergefrom? Other questions easily come to mind. Issimple awareness sufficient for a definition ofconsciousness or must consciousness include adeliberative component, i.e., is the only way weknow that we are conscious is by havingknowledge of what consciousness is? Why studyconsciousness at all if we already study perception,recognition, memory, thinking, decision-making,emotion, reasoning and similar topics sinceconsciousness should be nothing more than thesum and/or the emergent properties of thesecognitive processes?

What do we know about the neural substrate ofconsciousness? Well, we know that it helps to havea nicely functioning brain stem and related midlinestructures to be conscious at all and that there areboth imperfect behavioral and neurophysiologicalmeasures that can help us ascertain whethersomeone is conscious or not (e.g., not sleeping ordreaming or under anesthesia). We have otherbehavioral and neurophysiological measures thatcan help us ascertain whether within consciousnessa stimulus was attended to or neglected and to whatdegree the surface and abstract properties of thestimulus were adequately processed (both in andout of the person’s awareness). And we have a slewof behavioral and neurophysiological measures thatcan evaluate how competent a person is atabstractly analyzing a stimulus, scene, scenerio, orstory. Given this picture, it should be relatively easyto construct a hierarchy of consciousness from theessential neural components that provide thefoundation of consciousness (e.g., brain stem), tothose that allow the selective sensory processing of

external stimuli and internal cognitions (e.g., medialcortex, selected subcortical structures), and thosethat allow the processing and monitoring ofcomplex ideas and abstract knowledge (e.g.,prefrontal cortex). What is missing from thisconstruction is the temporal relationship betweenthe continuum of processing abilities (e.g.,sustaining conscious awareness long enough toadequately recognize the shape of a stimulus) andthe number of neurons in one or more neuralstructures or regions that allow for a particularprocessing level to be achieved. For example, ifthere were less than X number of neurons in avisual cortex region, no consciousness of a visualworld would be possible; if there were more than Xnumber of neurons in a region of visual cortex, wewould be able to process form crudely but with anadditional X number of neurons, we would be ableto process form capably and normally. This gradientof processing would indicate thresholds for certainkinds of consciousness and the kinds of fluctuationsthat might occur within a domain of consciousness(e.g., visual recognition).

Perhaps some researchers would find it moreimportant to divide consciousness betweenvolitional and a-volitional behavior or betweenautomatic and autonomous behavior rather thaninvestigating if one is simply conscious of theworld since they might claim that it is volitionaland autonomous behavior that distinguishes us ashumans? Alright then, but since being consciouspervades both sides of these arbitrary dividing linesto some degree, should our investigations require agreater focus on the “-ness” part of beingconscious? That is, should consciousness requireexplicit, autonomous behavior for its definition?Can we “expand” our consciousness in the sensethat we now are aware of something we weren’tbefore or we have a different understanding of asituation than we had before? Surely we can dothat but the act of expanding (or telescoping oreven blocking reflection in) our consciousness canbe described in the lexicon of the domain we arestudying whether it is attention, perception orproblem-solving.

Cortex, (2005) 41, 617-618

SPECIAL ISSUE: EDITORIAL

WHERE DOES CONSCIOUSNESS COME FROM?

Jordan Grafman

(Cognitive Neuroscience Section, National Institute of Neurological Disorders and Stroke – NINDS, National Institutes of Health – NIH, Bethesda, MD, USA)

No small matter choosing the right words torepresent what we mean by consciousness.Philosophers, computational modelers fromArtificial Intelligence, psychologists, historians,novelists, and any old human in the street may allhave a different way of describing the samephenomena. Of course we all search for a commonlanguage so we can have a common translationacross different disciplines. But that is not an easytask in the often, insulated world of academia anddisciplines may prefer using their own descriptionsfor many different reasons – not all related toscientific or academic pursuits.

Of course as humans we all have privilegedaccess to our own consciousness for the moment(who knows what future technologies will allow).This is not necessarily bad as we are all protectedand separated by the opaque veil of our ownexperience and of our own consciousness. Andperhaps that experience of opaqueness is whatmisleads us into thinking that something likeconsciousness is special and can be “localized.” Sowhere is it? Well my guess is that it is an emergentproperty or additive factor of literally all thedomains and sectors of the brain with specificbrain sections contributing different cognitive,sensory, and emotional components that as a wholecompose what we usually consider consciousness.Therefore, consciousness becomes an appropriatetopic for human factors study since a state ofconsciousness will change depending on aparticular set of circumstances, features, stimuli,intentions, and level of awareness. If the sameoverall set of brain structures that contribute tovarious cognitive processes are the same set ofneural structures making up consciousness-at leastin the way it is discussed by the authors of thisSection in Cortex, then it may be irrelevant forcognitive neuroscientists to study consciousness perse separately from the way they currently studycognition (e.g., the study of visual perception) andleave the notion of consciousness to socialpsychologists, sociologists, novelists or historianswho are concerned with the social processes thatenable the consciousness of an idea to be shared bymany.

But despite my caveats and questions, it isobvious that I am an amateur in this area of studyand I expect many of my questions and musings arejust simple naïve notions of what consciousness is.To remedy my naiveté we decided to include asection in this issue of Cortex devoted to describingcurrent ideas and research about consciousness withcontributions from physicians, psychologists,philosophers, and computational scientists. Sinceconscious consideration about consciousness is socontentious (now that was a mouthful), we haveadded commentaries for each of the papers as well

as an introduction by the Section editor GiorgioAscoli. Each of the main papers included somecommon themes although they are all unique intheir perspective. For example, all described a debtto philosophers in framing the major questions inconsciousness although none dared challenge thephilosophers’ precious and precarious position inthis regard. To a varying degree, some authorsattempted to decompose consciousness into variousstates, modules, and components but there was nota serious attempt to utilize existing cognitivescience frameworks for decomposition of cognitiveprocesses as a framework for examiningconsciousness. All the chapter authors dependedupon somewhat idiosyncratic points of view andnone discussed at any length the implications oftheir view of consciousness for the existence ofnon-human consciousness. Perhaps explicitly theconcern here was human consciousness and that isenough of a problem to grapple with withoutworrying about species that don’t communicate ona par with us. Most of the authors in this Sectiondeclared that self-awareness is a key forconsciousness but that appears to negate theconscious awareness that there are objects andstimuli that must be acted upon as a viable type ofconsciousness. Although if consciousness requiresan interaction between the world and the self, thensimpler forms of actions should qualify as a kind ofconsciousness. The relationship of prediction anderror monitoring to consciousness is also raised inthis Section with the idea that consciousness iscrucial to monitor and correct errors but does thatplace consciousness only in the prefrontal cortexand cingulate? Even patients with fronto-temporaldementia can display many forms of consciousbehavior despite their neuropsychological deficitsand lack of insight into their deficits or disease. Thecommentaries on each of the articles are valuablesince they have done a very nice job of pointing outsome of the weaknesses in each paper, neglectedthemes, as well as each paper’s most interestingpoints.

The avid reader of Cortex can assume that thesepapers reflect the current state of research onconsciousness. Do they demand we take aparticular route to its understanding? No. Do theygive us special insight into the nature ofconsciousness? Maybe. Do we better understandthe neural basis of consciousness having read thesepapers? Dare I say no. Do they suggest newmethods to study consciousness with? Yes. Do theyconvincingly tell us where consciousness comesfrom in the brain? Read on.

Jordan Grafman, Ph.D., Cognitive Neuroscience Section, National Institute ofNeurological Disorders and Stroke (NINDS), National Institutes of Health (NIH),Building 10, Room 5C205, MSC 1440, Bethesda, MD 20892-1440, USA.e-mail: grafmanj@ninds.nih.gov

618 Jordan Grafman