A presentation describing the neuroanatomy of hallucinations.

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The
Neurobiology of
Hallucinations.
UNDERSTANDING THE BRAIN:
THE NEUROBIOLOGY OF EVERYDAY LIFE
APOORVA MITTAL
INDIA
2019

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WHAT ARE HALLUCINATIONS?
§ The feeling of hallucination is just like the feeling of different senses (e.g.
touch, smell, taste, or seen and listen); almost a true feeling/realization. But
there is no substantive truth about any stimulation or realization or any
other objects. This is the particularity of hallucination. That is, despite
having any kind of substance, seeing or hearing or experiencing touch or
smell or taste. In other words, it can be said that experiencing something
which does not exist.
§ Many people confuse hallucination with imagination or thought. By
imagining or thinking, we can feel like an existent object or event or subject
and if we do not want to think about that again, we can stop thinking/feeling.
But it is not possible in the case of hallucination. Hallucination is not any
imagination! Nobody can have that feeling according to their will. Even
those feelings cannot be removed if anybody desires. It means that those
feelings are real.

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WHAT ARE HALLUCINATIONS?
§ Those feelings continue their own activities themselves. The affected
person has no influence or authority and control over them and he thinks
those feelings are real. For example, someone may see a person around
him; talking to him, touching him and he thinks the person as real. But in
reality no such person exists. Others cannot see that person or listen to the
person only the affected person can do. And that person will never believe
anybody on this earth if they try to convince him the reality. He will not trust
anyone rather he will be angry.
§ • It may also happen that the affected person can hear one or two or many
people. He may be sitting here but he is listening to someone from America.
He will never believe the truth as much as everyone refutes. Because it is
not a matter of logic rather it is an issue of disease and treatment. Some
people view them as miracles too.

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WHAT ARE HALLUCINATIONS?
§ In many cases, we see at the beginning of the disease or after a
few days of treatment, some patients, especially who are
intelligent, understand the matter that the experience that they
are having is not real. And then it becomes painful for him. Many
people cry a lot and they cry and do not want to listen to those
sounds that they hear. Some people even hit their head to the
wall too. These experiences are illusory and not a miracle at all
rather a grotesque feeling related to a disease.

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WHY DOES IT HAPPEN?
§ Why it happens is still not clear. However, there are lots of explanations on
the situations where hallucination can affect or cannot. Mostly it is related to
psychological problems or diseases. But hallucination can also affect in
some cases with physical problems. Hallucination is not a disease itself
rather it is a symptom of other diseases. So it is not possible to diagnose or
describe a specific disease by hallucination.
§ Mental disorders like schizophrenia, savior mood disorder and delusional
disorder often have hallucination as symptom. Addicted persons can also
be affected with different hallucinations. Physical problems like brain injury
can be the reason for hallucination too. Sometimes, people can have short-
term hallucinations due to the variation of salt.

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HOW DOES THE BRAIN BEHAVE?
§ Hallucinations are associated with structural and functional
abnormalities in primary and secondary sensory cortices. Reduced
grey matter in regions of the superior temporal gyrus/middle
temporal gyrus, including broca's area, is associated with auditory
hallucinations as a trait, while acute hallucinations are associated
with increased activity in the same regions along with
the hippocampus, parahippocampus, and the right hemispheric
homologue of broca's area in the inferior frontal gyrus. Grey and
white matter abnormalities in visual regions are associated with
visual hallucinations in diseases such as alzheimer's disease,
further supporting the notion of dysfunction in sensory regions
underlying hallucinations.

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HOW DOES THE BRAIN BEHAVE?
§ One proposed model of hallucinations posits that overactivity in sensory regions,
which is normally attributed to internal sources via feedforward networks to the
inferior frontal gyrus, is interpreted as originating externally due to abnormal
connectivity or functionality of the feedforward network. This is supported by
cognitive studies those with hallucinations, who demonstrate abnormal attribution of
self generated stimuli.
§ Disruptions in thalamocortical circuitry may underlie the observed top down and
bottom up dysfunction. Thalamocortical circuits, composed of projections between
thalamic and cortical neurons and adjacent interneurons, underlie certain
electrophysical characteristics(gamma oscillations) that are underlie sensory
processing. Cortical inputs to thalamic neurons enable attentional modulation of
sensory neurons. Dysfunction in sensory afferents, and abnormal cortical input may
result in pre-existing expectations modulating sensory experience, potentially
resulting in the generation of hallucinations.

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HOW DOES THE BRAIN BEHAVE?
§ Hallucinations are associated with less accurate sensory
processing, and more intense stimuli with less interference are
necessary for accurate processing and the appearance of
gamma oscillations(called "gamma synchrony"). Hallucinations
are also associated with the absence of reduction in P50
amplitude in response to the presentation of a second stimuli
after an initial stimulus; this is thought to represent failure to gate
sensory stimuli, and can be exacerbated by dopamine release
agents.

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10. z
z AUDITORY
HALLUCINATIONS
IN
SCHIZOPHRENIA

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TREATMENTS
§ There are few treatments for many types of hallucinations. However, for
those hallucinations caused by mental disease, a psychologist or
psychiatrist should be consulted, and treatment will be based on the
observations of those doctors. Antipsychotic and atypical
antipsychotic medication may also be utilized to treat the illness if the
symptoms are severe and cause significant distress.[citation needed] For
other causes of hallucinations there is no factual evidence to support any
one treatment is scientifically tested and proven. However, abstaining
from hallucinogenic drugs, stimulant drugs, managing stress levels, living
healthily, and getting plenty of sleep can help reduce the prevalence of
hallucinations. In all cases of hallucinations, medical attention should be
sought out and informed of one's specific symptoms.

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FURTHER READING AND
REFERENCES
§ https://en.wikipedia.org/wiki/Hallucination#Pathophysiology
§ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2702442/
§ https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ca
d=rja&uact=8&ved=2ahUKEwj-k-
O_rKrhAhWC8XMBHQXJCW4QFjABegQICRAB&url=https%3A%2F%2Fw
ww.ncbi.nlm.nih.gov%2Fpubmed%2F16362846&usg=AOvVaw0beNzYGgt8
UzBuYCx-RFFj
§ https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=8&ca
d=rja&uact=8&ved=2ahUKEwj-k-
O_rKrhAhWC8XMBHQXJCW4QFjAHegQIBhAC&url=http%3A%2F%2Fme
dind.nic.in%2Ficg%2Ft09%2Fi2%2Ficgt09i2p119.pdf&usg=AOvVaw2iwn4_I
3tQ9fEQLwZJzHOJ

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FROM THIS COURSE
§ Professor Mason has elegantly explained all the concepts and
her enlightening lectures have been a great step into getting
more affiliated with a field of science that is great part of our
daily life.
§ This course has inspired me to research different brain disorders
and be compassionate to the people who suffer with brain
disorders
§ This course has helped me to appreciate how blessed I am with
health and do everything possible to maintain it. I also want to
help those around me.

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THANK YOU!