The trend in the literature on fetal pain is to approach the question of consciousness in the fetus in terms of conscious states of pain. That is, first define what makes a pain a conscious mental state, and then determine being a conscious fetus in terms of having such a state. Thus, the possibility of a conscious fetus is thought to rely on theories of conscious pain states. Call this the state approach to fetal pain.
Two state approaches to fetal pain are present in the literature. One approach looks at the brain structure(s), pathways and circuits necessary for conscious pain states and then seeks to establish whether this substrate is present and functional in the fetus. There is broad agreement among researchers that the minimal necessary neural pathways for pain are in the human fetus by 24 weeks gestation [1, for review]. Some researchers argue that the fetus can feel pain earlier than 24 weeks because pain is enabled by subcortical brain structures [4,5,6].
Another phenomenal approach is to consider the subjective content of a conscious experience of pain, and to ask whether that content might be available to the fetus [1,2,3]. Based on this approach, some researchers argue that the fetus cannot feel pain at any stage because it lacks developmental abilities and concepts such as sense of self necessary for pain [1,2,3].
Although both state approaches are presented as opposites in the literature, they share the determination of fetal pain based on specific levels or degrees of complexity, whether of the brain structures and the relationship they have to the conscious state of pain, or of the subjective contents that constitute that state.
An alternate approach to understanding fetal consciousness that has not been explored in the literature on fetal pain is the extent to which pain is based on the arrangement of certain brain structures (or experiential contents), rather than a result of maturation or increase in complexity achieved by growth of the brain substrate which below a certain size does not enable consciousness [7,8]. Thus, whether the fetus is excluded in this regard is not due to its simplicity, but because its lack of certain brain arrangements necessary to enable consciousness.
According to this alternate view of fetal pain, a living creature’s subjective contents may differ greatly in complexity. To convey the range of conscious possibilities, consider the Indian ‘scale of sentience’ (cited in [8]):
‘This.’
‘This is so.’
‘I am affected by this which is so.’
‘So this is I who am affected by this which is so.’
The possibilities in this consciousness scale range from simply experienced sensation (‘This’; ‘This is so’) to self-consciousness (‘I am affected by this which is so’; ‘So this is I who am affected by this which is so’). Each stage in this scale presupposes consciousness. Any experience, whatever its degree of complexity, is conscious. It follows that to see, to hear, and to feel is to be conscious, irrespective of whether in addition a creature is self-conscious that it is seeing, hearing, and feeling [7]. To feel pain is to be conscious of that experience regardless of whether in addition one is self-conscious of being in pain. Self-consciousness is just one of many contents of consciousness available to big-brained living creatures with complex capacities: it is not definitive of consciousness [7,8]. The point of saying this is that it circumvents the logical mistake of misidentifying attributes unique to a specialized form of consciousness (e.g., self-consciousness) as general features of consciousness itself.
With this alternate view of consciousness now sketched in, we should determine where the fetus and where pain fall in the Indian scale of sentience. The possibilities in the scale extend from mere sensation to self-consciousness–where does the fetus fall in?
References
[1] Derbyshire S, Raja A. (2011). On the development of painful experience.Journal of Consciousness Studies, 18, 9–10.
[2] Derbyshire SW. (2006). Controversy: Can fetuses feel pain?. BMJ: British Medical Journal, 332(7546), 909.
[3] Szawarski Z. (1996). Do fetuses feel pain? Probably no pain in the absence of “self”. BMJ: British Medical Journal, 313(7060), 796–797.
[4] Anand KJ, Hickey PR. (1987). Pain and its effects in the human neonate and fetus. New England Journal of Medicine, 317(21), 1321–1329.
[5] Anand KJ. (2007). Consciousness, cortical function, and pain perception in nonverbal humans. Behavioral and Brain Sciences, 30(01), 82–83.
[6] Lowery CL, Hardman MP, Manning N, Clancy B, Whit Hall R, Anand KJS. (2007). Neurodevelopmental changes of fetal pain. In Seminars in perinatology (Vol. 31, No. 5, pp. 275–282).
[7] Merker B. (1997). The common denominator of conscious states: Implications for the biology of consciousness. Available at: http://cogprints.soton.ac.uk.
[8] Merker B. (2007). Consciousness without a cerebral cortex, a challenge
for neuroscience and medicine. Target article with peer commentary and author’s response. Behavioral and Brain Sciences, 30, 63–134.
Simon van Rysewyk 