Human consciousness: from fetal to neonatal life

The beginning of human personhood is the moment when a human is first recognized as a person. There are differences of opinion as to the precise time when human personhood begins and the nature of that status. The issue arises in a number of fields including science, religion, philosophy, and law, and is most acute in debates relating to abortion, stem cell research, reproductive rights, and fetal rights.

The fetus may be aware of the body, for example by perceiving pain. It reacts to touch, smell, and sound, and shows facial expressions responding to external stimuli. However, these reactions are probably preprogrammed and have a subcortical nonconscious origin.

Furthermore, the fetus is almost continuously asleep and unconscious partially due to endogenous sedation. Conversely, the newborn infant can be awake, exhibit sensory awareness, and process memorized mental representations. It is also able to differentiate between self and nonself touch, express emotions, and show signs of shared feelings.

Yet, it is unreflective, present oriented, and makes little reference to concept of him/herself. Newborn infants display features characteristic of what may be referred to as basic consciousness and they still have to undergo considerable maturation to reach the level of adult consciousness. The preterm infant, ex utero, may open its eyes and establish minimal eye contact with its mother.

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It also shows avoidance reactions to harmful stimuli. However, the thalamocortical connections are not yet fully established, which is why it can only reach a minimal level of consciousness.

Stages of human life during pregnancy

(Conception to a two-week old embryo)

About 3 days after conception: The zygote now consists of about 16 cells and is called a morula (a.k.a. pre-embryo). It has normally reached or exited the fallopian tube and entered the uterus.

5 days or so after conception: The grouping of cells are now called a blastocyst. A cavity appears in its center. It has an inner group of cells which will become the embryo and later the fetus, and still later the newborn. It has an outer shell of cells which will “become the membranes that nourish and protect the inner group of cells.” It has traveled down the fallopian tubes and has started to attach itself to the endometrium, the inside wall of the uterus. The cells in the inside of the blastocyst, called the embryoblast, start forming the embryo. The outer cells, called the trophoblast, start to form the placenta. 4 The blastocyst is often referred to as a “pre-embryo.”

9 or 10 days after conception: The blastocyst has fully attached itself to endometrium — the inner lining of the uterus. Primitive placental blood circulation has begun. This blastocyst has become one of the lucky ones. The vast majority of ova are never fertilized, don’t make it this far in the process and are ejected from the uterus.

12 days or so after conception: The blastocyst has started to produce unique hormones which can be detected in the woman’s urine. This is is the event define to be the start of pregnancy. If instructions are followed exactly, a home-pregnancy test will reliably detect pregnancy at this point, or shortly thereafter.

13 or 14 days after conception: A “primitive streak” appears in the embryo. It will later develop into the fetus’ spinal colum. This is the point at which spontaneous division of the blastocyst — the process by which identical twins are developed — is not longer possible. The pre-embryo is now referred to as an embryo. It is a very small cluster of undifferentiated cells at this stage of development. It has no functioning brain; it has no internal organs; it is not conscious at this stage, or for many months afterwards.

Newborn sensory awarenes

The newborn infant exhibits in addition to sensory awareness specially to painful stimuli, the ability to differentiate between self and nonself touch, sense that their bodies are separate from the world, to express emotions, and to show signs of shared feelings. Moreover, “objective signs” for the mobilization of the GNW circuits are being detected in awake infants at the level of the prefrontal cortex in sensory processing, in responses to novelty and to speech and in social interaction. Yet, its capacities for internal manipulations in working memory are reduced, it is unreflective, present oriented and makes little reference to concept of him/herself. Newborn infants display features characteristic of what may be referred to as basic or minimal consciousness. They still have to undergo considerable maturation to reach the level of adult consciousness.

The preterm infant ex utero may open its eyes and establish a minimal eye contact with its mother. It also shows avoidance reactions to harmful stimuli. The connections with the GNW circuits are not yet fully established. Our view is that it has reached only a lower level of minimal consciousness analogous (though, of course, not identical) to that of a rat/mouse. A pending question is the status of the preterm fetus born before 26 wk (<700 g) who has closed eyes and seems constantly asleep. The immaturity of its brain networks is such that it may not even reach a level of minimal consciousness. The postnatal maturation of the brain may be delayed and there are indications that the connectivity with the GNW will be suboptimal in some cases as indicated by deficient executive functions. Therefore, the timing of the emergence of minimal consciousness has been proposed as an ethical limit of human viability and it might be possible to withhold or withdraw intensive care if these infants are severely brain damaged.
Credit :

Swedish Science Foundation and Stftelsen Ragnar och Torsten

NCBI – National Center For Biological Information

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