Most consistently implicated are various areas of the lateral and medial prefrontal cortex, but activations are also reported in the parietal cortex and insular cortex ( Fig.

For example, when self-reports of the stimulus are compromised by using subliminal stimulation procedures, such as masking ( 63), areas of the visual cortex (including primary and secondary areas) are functionally active, but when participants are able to consciously report seeing a visual stimulus, additional cortical areas become active ( 47, 54, 64– 71). This does not mean that defensive survival circuits play no role in conscious fear: they modulate the experience of fear, but are not directly responsible for the conscious experience itself.Įvidence has mounted in recent years implicating specific brain circuits in introspectively reportable conscious experiences of visual stimuli in humans. These findings all suggest that the amygdala-defensive survival circuits processes threats nonconsciously ( 8, 9, 20). Fourth, although damage to the amygdala interferes with bodily responses to threats, it does not interfere with conscious experience of emotions such as fear ( 43, 44). Third, “blindsight” patients, who lack the ability to consciously see visual stimuli in a particular area of visual space, exhibit amygdala activation and physiological responses to visual threats presented in that part of space despite denying seeing the stimulus and without reporting fear ( 40– 42) (see SI Appendix, Box 2 for a discussion of blindsight and other neurological patients that have contributed to consciousness research). Under such conditions, participants do not report feeling fear, even when explicitly instructed to be introspective about what they are experiencing ( 39). Second, studies using subliminal stimulus presentation methods (e.g., backward masking or continuous flash suppression) to prevent or reduce awareness of visual stimuli show that visual threats activate the amygdala and elicit body responses despite the fact that participants deny seeing the stimulus ( 21– 30). If the same circuit was involved the correlation should be strong. First, it is well established that conscious feelings of fear and anxiety are poorly correlated with behavioral and physiological responses, such as those controlled by defensive survival circuits ( 38). That the defensive survival circuit is separate from the circuit that gives rise to the conscious experience of fear is suggested by several lines of evidence. This approach allows animal research to be relevant to the human experience of fear, but leads to much confusion about what researchers mean when they use the term “fear” ( 20, 35). It is, in fact, common in behavioral neuroscience to construe animal and human behavior as being caused by so-called central states rather than by subjective experiences, while at the same time retaining the subjective state term ( 13, 16– 18, 34). Others, like Perusini and Fanselow ( 31), agree that danger elicits fear and fear causes behavior, but they do not treat it as a subjective experience for them, fear is a brain state that intervenes between threats and defensive behaviors. Panksepp ( 5) noted that “fear is an aversive state of mind,” the major driving force of which is a “subcortical FEAR system” ( 33). Mowrer ( 32) argued that rats freeze “by cause” of fear. Darwin ( 1), for example, called emotions like fear states of mind inherited from animals. For some, fear is a subjective state, a phenomenal experience elicited by danger. For example, although temporality and selfhood may be correlated, they are different concepts: it is conceivable that an animal could have a richly temporally integrated stream of experiences without any awareness of itself as the subject of those experiences, and it is conceivable that an animal could have temporally fragmented ‘staccato’ experiences while being aware of itself as the subject of those fragments.What is meant by “fear” varies among those who use it to account for behavioral and physiological responses to threats. We have tried to ensure that our dimensions are conceptually distinct. It does, however, matter that the dimensions are conceptually distinct from each other (that they are not the same thing described in two different ways). This is a hypothesis worthy of further investigation. For example, it may turn out that temporality is correlated with selfhood, because richer forms of temporal integration enable a species to evolve a higher grade of self-consciousness. If one dimension is found to correlate positively with another, this is an interesting result, not a problem. What is not required is that the dimensions should be completely uncorrelated. A second challenge is to make sure the dimensions are distinct enough from each other.

Sentience vs consciousness