Memorandum 4
Submission from Dr Stuart Derbyshire,
University of Birmingham, School of Psychology
EVIDENCE REGARDING
THE DEVELOPMENT
OF FETAL
PAIN
EXECUTIVE SUMMARY
The issue of fetal pain is divided into two
component parts: the first addresses the developing neurobiology
of the fetus and the second the developmental psychology of pain.
With regards to neurobiology, there are a series of important
points in development that may be relevant to pain processing.
New features have been observed at 7, 18 and 26 weeks gestation
and used to suggest an experience of pain in utero. These
new features are tremendously interesting, and exciting, but they
do not tell us that the fetus is capable of pain experience. Subjective
experience, including pain, cannot be inferred from measures of
anatomy, stress hormones and fetal movements because these measures
do not account for the contents of experience in general, and
of pain in particular. Before an infant can think about objects
or events, or experience sensations and emotion, the elements
of thought must have their own independent existence in the infant's
mind. This is something that is achieved via continued brain development
in conjunction with discoveries made in action and in patterns
of adjustment and interaction with the infant's caregiver. We
can be confident that the fetus does not experience pain because
the developmental processes necessary for experience are not yet
developed. Consequently, anaesthetic intervention during abortion
is unnecessary and discussion of fetal pain with women seeking
a termination unhelpful. Nevertheless, absence of fetal pain does
not resolve the question of whether abortion is morally acceptable
or should be legal.
ABOUT THE
AUTHOR
The author has been actively involved in the
use of brain imaging techniques since these techniques were first
applied to the assessment of pain in 1991. He has a particular
interest in the relation of biological measurements to psychological
experience and has consequently contributed to debate on fetal
pain. These contributions have included published reviews in the
British Medical Journal, the journal Bioethics and the journals
of the International Association for the Study of Pain and the
American Pain Society as well as oral testimony before UK and
USA Government and scientific bodies. The author is a member of
the International Association for the Study of Pain and the American
Pain Society.
1. This paper examines two main issues: first
the neurobiology of the fetus and second the difficulty of bringing
together the biological development of the fetus with the notion
of fetal pain. On the first, the key point is that there are a
series of important moments in development that may be relevant
to pain processing. Fetal development is continuous, of course,
but new features have been observed at 7, 18 and 26 weeks gestation
and have been used to suggest an experience of pain in utero.
These new features are tremendously interesting, and exciting,
but they do not tell us that the fetus is sentient. It is a mistake
to try and read off experience, including pain, from measures
of anatomy, stress hormones and fetal movements, because this
approach fails to account for the contents of awareness in general,
and of pain in particular.
A. THE NEUROBIOLOGY
OF A
FETUS
2. Although the analogy is quite oversimplified,
it is not unreasonable to think of pain as being similar to a
fire alarm. The pain stimulus is the same as hitting the red button,
the electric cable to the alarm is the same as the connection
between nerve endings and the brain and the alarm itself is the
brain ringing out pain. Answering the question of whether the
fetus feels pain can then be answered, in part, by considering
the development of this "alarm" system.
3. First, the "alarm buttons":
Fetal skin contains free nerve endings, naked nerve endings that
lie free in the skin, responsible for initial registration of
noxious stimulation. Although these begin to form from about 7
weeks gestation, these cells do not mature until 24-28 weeks gestation.
The spinal cord, the major "cable" from the "buttons"
to the brain, also does not mature until around 24-28 weeks.
4. Some projections from the immature spinal
cord reach the thalamus (the lower "alarm") of the brain
at about 7 weeks gestation but at 7 weeks the nervous system is
very immature. It is not yet ready to "ring". There
is little indication of the cell structure and mature organization
of the spinal cord, thalamus or cortex, which will gradually appear
from around 20 weeks gestation.
5. The very first projections from the thalamus
towards the cortex (the higher "alarm") are apparent
from about 12-16 weeks gestation but these are projections into
the subplate. The subplate is a "waiting compartment"
where fibers accumulate and mature before penetrating the cortical
plate developing above. Like waiting in the lobby of a theatre
or stadium, interactions are random, and uncoordinated, until
direction towards a seat is provided.
6. From 18 weeks, studies have demonstrated
that the fetus can launch a "stress response" to invasive
procedures including increased production of cortisol and ß-endorphin.
Other defensive reactions, such as the redistribution of blood
towards vital organs, have also been described. These reactions
are indicative of a maturing brain and nervous system, reflected
in the anatomical changes described. It is noteworthy, however,
that these haemodynamic changes and changes in cortisol and endorphins
are elicited at the subcortical and brainstem level and do not
require cortical input and thus do not provide evidence for pain
experience. Cortisol and endorphin are significantly elevated
during surgical procedures carried out under general anesthesia,
and in brain dead patients during organ harvesting, despite cortical
activation in these patients being profoundly suppressed.
7. Thalamic connections do not penetrate
the cortical plate, making it to their "seats", until
26 weeks gestation. The "alarm" has now been built to
ring though with considerable development of its "ringing"
ability yet to be realized.
8. Starting at 28 weeks there is massive
relocation of subplate fibers into the cortical plate. Even after
that point the cortical plate undergoes tremendous growth increasing
in volume by 50% between 29 weeks and term when the characteristic
layers, the "seat ordering", of the cortex appear.
9. There can be no question that fetal development
is both rapid and amazing but there is equally no question that
the fetus is immature. The cell structure of the immature brain
differs from that of a mature one to a considerable extent and
the fetal brain has a number of prominent structures that are
transient in nature. For example, the thalamic reticular nucleus,
which is attached to the side of the thalamus, appears as inconspicuous
in the adult human brain but is very prominent in the fetal brain.
In the fetal brain, this reticular nucleus is characterized by
a high packing density of neurons, which undergo cell death after
birth. These cells are likely involved in the regulation of developmental
events in the womb that become unnecessary after birth.
10. One function of such cells could be to
suppress fetal arousal through inhibition of thalamocortical activation.
Suppression of fetal arousal in the womb is also known to involve
placental inhibitory factors, such as adenosine, and other neurotransmitters,
peptides and endocrine factors as well as the warmth, buoyancy
and cushioned tactile environment provided by the womb. The intense
tactile stimulation during labor, and the subsequent separation
of the baby from the placenta and umbilical cord, facilitates
the usually rapid onset of behavioral activity and wakefulness
in newborn human infants. The function of some neurotransmitters
and hormones will switch at this point and the structure of the
brain will begin a new phase of change and development—often
as rapid and as impressive as changes during the fetal period.
11. To summarize this section on the structure
and function of the fetal brain: while it is obviously true that
the fetus undergoes tremendous development from conception to
birth, extrapolation from the mature to immature brain and even
from the post natal environment to the womb are bound to be approximate
and often mistaken.
B. THE DIFFICULTY
OF BRINGING
THE FETUS
AND PAIN
TOGETHER
12. To a large extent, however, the biological
development of the fetus is beside the point because the mere
presence of anatomical structures, neurochemicals, hormones, and
so on, is insufficient for experience, including that of pain.
13. Pain is not merely the response to physical
injury or disease but is a higher order experience including emotional,
cognitive (thinking) and sensory components. It is not something
that we experience raw and then interpret post-hoc. The interpretation
is the experience. Distinguishing sensations from thoughts, emotions,
or each other requires a conceptual basis on which the distinction
is drawn. We easily forget that this conceptual basis is needed
and view brain development as merely about hooking "alarms"
up to "buttons", forgetting that it is also about enabling
subjective experience.
14. At birth and afterwards there is a massive
increase in sensory input and this acts as a form of "neuronal
crowd control". Repeated sensory input during this critical
period of development results in generation and stabilization
of functional brain circuits with unused pathways being eliminated.
This internal organization of inputs helps the differentiation
and creation of feeling so that the feeling of hunger, for example,
can be separated from feelings of cold.
15. Prior to this organization everything
will arrive at the senses in an undifferentiated form, like looking
at a vast TV screen with the world's information upon it from
a distance of two centimeters. A great buzzing mass of meaningless
information. What needs to happen before an infant can think about
objects or events, or experience sensations and emotion, is that
the elements of thought must have their own independent existence
in the infant's mind. This is something that is achieved post-birth
both via continued brain development and through discoveries made
in action and in patterns of mutual adjustment and interaction
between infant and caregiver. Changes in frontal cortex activity,
for example, come at a time when cognitively related behaviors,
such as the phenomenon of stranger anxiety and improvements in
memory begin to appear. Similarly the first coordinated motor
movements require the further development of specialized motor
regions of the brain. Gradual improvements in motor, visual, spatial
and sensory integration mark the disappearance of reflex neonatal
behaviors and the emergence of higher conscious function, which
will include pain.
16. The development of representational memory,
which allows an infant to respond and learn based upon stored
information rather than upon the basis of material directly available,
may be considered a building block, if not a cornerstone, of conscious
development. This function begins to emerge between 2 and 4 months
of age. From now on there is the possibility of tagging in memory,
or labeling as a `something', all the objects, emotions and sensations
that appear or are felt. As the infant develops, identifies with
others, and is affected by their reactions, so her behavior becomes
increasingly guided by the push and pull of her inside and outside
world until the two become intertwined allowing understanding
and thinking to flourish. When this happens, everything is changed.
17. Concepts, thought and language now become
possible. Language plays a particularly important role because
it is largely through language that true concepts or thoughts
can arise as words, or other symbols, are used to encompass those
thoughts. Language quite probably slots into those patterns of
interaction and mutual adjustment between infant and caregiver
that have been well practiced for many months. But now language
allows for a level of distinction and refinement in thinking that
would otherwise not be possible. To have and to use a concept,
one needs to have it and use it consistently and appropriately.
I cannot privately point to an object or identify an emotion and
expect to gain reliable information. To reliably discriminate
the world, one needs to be able to check that the concept is being
used correctly and not at whim. For this, one needs a way of checking
and it is here that other people and language come into the picture.
18. Subjective experience might feel entirely
natural and private but this is mistaken. The content of our mind
becomes meaningful to us only in so far as it is meaningful to
others and is the consequence of a developmental process that
is social as well as natural. If pain, for example, were an entirely
private affair, no words would be able to express it because no
external frame of reference would be comparable and therefore
adequate to express the sensation. Pain is not like this because
clearly people do express their painful experiences and these
expressions have meaning that allow for diagnosis, treatment and
eradication of pain. The expressions of pain are meaningful because
they are attached to publicly accessible conditions that warrant
their application. If we were trapped inside our own heads, we
would be unable to know whether what one person states as "pain"
is the same as someone else's "pain". Indeed we would
not know if any internal state of our own were the same or different
from any other and, as it would not be possible to distinguish
any state from any other, no state would consequently exist. This
is not to deny that the neonate and fetus has the neural apparatus
to discriminate information; clearly the fetus and neonate do
not respond to tactile stimuli in the same way as to visual stimuli,
for example. Indeed, this discriminatory processing is the raw
material for a primary caretaker's assessments of need and for
the interactions and behavioral adjustments that will occur in
the forthcoming months. But it is to deny that there is experiential
discrimination and, therefore, that there is experience at all.
19. Conscious experience only begins as objects,
events and emotions become a focus between the infant and caregiver.
Discoveries are made first in mutually coordinated actions and
feelings rather than in thought. In so far as human beings live
in a community of thinking, feeling, talking beings these things
that happen between people then become things that happen within
the individual's own mind and the privacy of experience is broken
down and externalized for further analysis. As we are able to
externalize our inner world so we are able to reflect upon that
world and become self aware or self-conscious. Consciousness is
self-consciousness, one cannot reflect upon the world without
knowing that it is I who am reflecting. If we were not conscious
of being conscious, then we would be unconscious of consciousness,
which is an absurdity. It is social development and language that
make this conscious awareness possible; symbolic representation
does not teach an infant to recognize differences that were always
there it teaches them to create differences where none previously
existed. This, of course, sounds very strange—We instinctively
want something, such as neuroanatomical features or pain behavior,
to be the disinterested representation of the pain sensation.
We are constantly trying to strip off the social elements of the
pain experience to get at its true biomedical core but we have
no access to this core pain sensation; it simply does not exist
within the bounds of our awareness. It is only with content that
experience becomes realized and content is not natural. The temporal,
sensorial, affective and cognitive features of pain are things
that we spend a great deal of our development learning.
20. Language plays a particularly important
role, not by giving voice to experiences already available and
fully formed inside our heads, but by creating those subjective
experiences through making the quality of those experiences apparent
to us, by giving them a structure, by placing them within more
abstract categories of thought and by linking them to external
reference and social convention. Clearly our access to others'
pain is mediated through behavior and language but this is also
true of our own pain experience. Social development structures
our behavior and language so as to be meaningful to the outside
world but with the unnoticed side effect of rendering the child's
inner experience meaningful to him or her. While brain development
is certainly a necessary precursor of conscious sensory awareness,
merely peering inside the head will not reveal the source of awareness.
21. This is how we can be so positive that
the fetus is not conscious and, therefore, cannot experience pain.
Not only has the biological development not yet occurred but also
the post-birth environment, so necessary to the development of
experience, has not yet made itself felt. In short, fetal pain
is a moral blunder based on the false equivalence between observer
and observed that misses the whole point and process of development.
22. One final point in conclusion. Regardless
of what we can prove, or what we believe, about fetal capabilities,
there will never be a fetalometer to tell us whether an act of
violence against the fetus is right or wrong. Abortion is a legal
question, a political question and a moral question but it is
not a scientific question. Consequently it needs to be decided
at the level of society and morality and not with science.
August 2007
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