Consciousness is defined as the state of being aware of oneself and the environment, as well as the awareness of internal and external existence. Consciousness is experienced by humans constantly, from a summer breeze to a heartbreak, we are aware of it all. Everyone’s consciousness is unique to them, with everyone having different memories, sensations, and feelings. Some believe that humans are the only conscious animal, whereas others believe that other animals have the ability to be conscious too.
There are two normal states of consciousness, defined as unconscious and conscious. Consciousness can also be altered by medical or mental conditions. Some of these can include lethargy, delirium, coma, and confusion.
Are humans the only conscious animal?
Whilst consciousness cannot be fully defined nor observed, it is thought that the source lies within brain structure and function. Like humans, animals such as reptiles and fish switch between being awake and sleeping, with circadian rhythms just like ours. Certain portions of the brain control the waking and sleeping states. So, if consciousness is defined as being awake rather than asleep, the majority of animals would be classified as conscious.
However, if consciousness is defined as being aware of oneself with an understanding of emotions, are humans alone in this? It has been determined that non-human animals such as mammals and birds have the required neurological substrate complex to allow them to have conscious experiences. As this has been determined, the study can move away from determining whether animals are conscious or not and towards determining which animals are conscious.
Of course, it is difficult to determine whether an animal is conscious or not as they cannot verbally communicate with humans to detail their experiences. However, nor can human infants, and these are thought to be completely conscious of the world around them, and capable of forming memories and associations. Currently, the level of animal consciousness is being researched, to determine whether some animals are more conscious than others.
Theories for the basis of consciousness
It is thought that in vertebrates, consciousness is an integrated and complex process partly controlled by events in the forebrain. It is suggested that the neural mechanisms involved in consciousness were chosen during evolution as they enable animals to plan for future eventualities. There is evidence to support the implication of the thalamus and cerebral cortex in consciousness. However, the removal of these structures does not always mean an animal is unconscious. Consciousness has been shown to continue despite large portions of the brain having been damaged and lost. Interestingly, whilst the loss of the cerebellum and frontal cortex does not necessarily mean unconsciousness, the destruction of thalamic nuclei is strongly associated with a permanent loss of consciousness.
Some scientists have argued that human consciousness uses widespread interactions between the thalamus and the cortex, termed thalamocortical loops. A specific type of neuron called a cortical layer 5 pyramidal (L5p) neuron is thought to be involved in these loops and play a role in consciousness. These neurons are thought to send output signals to both the thalamus and the cortex.
A way to further consider the nature of consciousness is to look at unconsciousness. For example, anesthetics have been studied, looking at the way they induce unconsciousness. It has been found in mice that general anesthesia decreases the coupling of certain nerve cell activity to firing in the L5p neurons. This, therefore, implements the L5p neurons in consciousness, though it is not known which group of them is involved.
Whilst it is strongly suggested that loops and L5p neurons are involved in consciousness, it is difficult to determine if they have a true effect, or what is specifically responsible for different elements of consciousness.