Neural Circuitry of the AIC. If our brains were simple enough to be understood, we wouldn t be smart enough to understand them

Size: px

Start display at page:

Download "Neural Circuitry of the AIC. If our brains were simple enough to be understood, we wouldn t be smart enough to understand them"

Edgar Young
5 years ago
Views:

1 Neural Circuitry of the AIC If our brains were simple enough to be understood, we wouldn t be smart enough to understand them

2 Thesis! An analysis of the various neural connections of the Anterior Insular Cortex based on function and interaction with other brain structures. This analysis establishes possible connections between the Anterior Insular Cortex, Anterior Cingulate Cortex, Dentate Gyrus, Amygdala, Prefrontal Cortex, Superior Temporal Gyrus, Cerebellum, Gut, Fusiform Gyrus, Somatosensory cortex and the Supplementary Motor Cortex.

3 Abstract! In this presentation we will attempt to draw out various possible circuitry involving the Insular cortex.! We will highlight connections which have already been established such as that between the AIC and ACC! We have also inferred and referenced several neural pathways in which the Insular Cortex is involved.! A lot of our findings are mere speculation and have not been supported by facts.! The purpose of this project is to establish the biological pathways which involve the IC

4 Intro! The Insular cortex is responsible for an array of diverse functions which is what defines us as human beings.! Located towards the anterior ventral region of the brain, it can be located by splitting the Sylvian fissure at the junction of the frontal, parietal and temporal lobes.! For long the Insular Cortex has been credited with the functions of Interoception and Empathy.! They are also known to house the rare Von Economo neurons which have been related to higher levels of self awareness.! There is a well established connection between the AIC and ACC which is mediated by Von Economo neurons

5 AIC Morphology! The Insular Cortex is found in the Cerebral Cortex, near the Sylvian Fissure! It is somewhat pyramid shaped and divided into two lobes, left and right which are roughly symmetrical and are majorly contralateral.! The Insular Cortex is divided into 2 parts: the Anterior Insula and the Posterior Insula! The Anterior Insular Cortex is larger than the Posterior Insular Cortex! The Operculum (lid) is formed by the Frontal Lobe, Temporal Lobe, and Parietal Lobe as the overlap the area that creates the Insular Cortex! Both lobes have an intricate ventricular system with around 96 arteries branching into the two lobes.

7 AIC Functions! Empathy- The ability to correlate with the feelings of other human beings! Self Awareness- The spatial awareness of ones self or consciousness! Interoception! Spatial Awareness! Complexities of emotion

AIC Circuitry Since the AIC is involved with higher cognitive and emotional functions it makes sense that it is connected to the Hypothalamus and the Thalamic Nuclei.

8 AIC Circuitry Since the AIC is involved with higher cognitive and emotional functions it makes sense that it is connected to the Hypothalamus and the Thalamic Nuclei. In the AIC signals are routed from the Thalamic Nuclei to the posterior insula. Between the posterior insula and the anterior insula, signals are rewired and translated. This translation possible happens due to the presence of Von Economo Neurons. The new electrical signals are processed in the AIC and transported to other cortical structures. Among these structures the most evident are the Anterior cingulate cortex, dorsolateral prefronatal cortex and the amygdala.

9 AIC ACC Circuit! As research continued throughout the years, scientists were able to draw the conclusion that the Anterior Insular Cortex and the Anterior Cingulate Cortex work in tandem with one another.! A. Craig found that activation in the AIC also triggered a response in the ACC, showing the direct correlation between the two regions of the brain.! Many studies suggest strong functional connectivity between the brain regions although the conclusion that information exchange is taking place, can not be proven.! As recent studies have shown, Von Economo Neurons are present in both of the anterior cortices.

Von Economo Neurons! Previously known as the Spindle Neuron, the Von Economo Neurons are only found in the 5 th layer of 7 layers in the Anterior Cortices.

11 Von Economo Neurons! Previously known as the Spindle Neuron, the Von Economo Neurons are only found in the 5 th layer of 7 layers in the Anterior Cortices.! * Von Economo Neurons are also found in the dlpfc (Dorsal Lateral Prefrontal Cortex).! In the ACC its functions include: Motor abilities, digestion, heart rate, and judgment.! In the AIC its functions include: Spatial awareness, sense of touch, self awareness, and complexities of emotion.! Von Economo neurons contain Setratonin 1 and D3 D5 receptors.

12 Insulo-Amygdalar connection! In a study completed in 1999, author, AJ McDonald, found that the insular cortex had an explicit connection with the CXA (Central Extended Amygdala).! Most of these signals are from the gustatory and viscerosensory dysgrannual segments of the AIC.! * Signals also arise from the Somatosensory Posterior Insular Cortex! These projections also target subsets of the CXA structures that have been innervated by the insular cortex.! McDonald found that the projections from the IC were very dense in the lateral half of the CL (Central Nucleus) and less dense in the medial half of the CL.

13 Dopamine Receptors and Function! Most neurotransmitter receptors in the Insular cortex are dopaminergic in nature. Seratonergic receptors are also present but their concentration is bleak as compared to the of dopamine.! Dopamine in the brain is synthesized by the Substantia Nigra par Compacta in the Basal Ganglia.! From here the inhibitory channel continues to the striatum, Gpi, SNr and the Thalamus. From there it moves into the cortex of the basal ganglia.! Since the primary neurotransmitter in the Insular cortex is an inhibitor we can relate to its function of the halt mechanism.! The inhibitory Dopamine is also affected by schizophrenia and hence could explain why the AIC is affected.! Dopamine concentration in the AIC is also indicates that Spatial Awareness and Empathy are inhibitory functions rather than excitatory and hence our state of consciousness is essentially a regulation of inhibition and not excitation.

14 Cont! Mesolimbic Pathway (positive symptoms)- this projects into ventral tegmented area and nucleus accumbens.! Mesocortical Pathway (Hypoactivation)- Projects into the Ventral Tegmented area and the prefrontal cortex. This is associated with the negative symptoms of Schizophrenia. (cognitive and emotional functions are affected)! Nigrostriatal Pathway- (pseudoparkinism) From Substantia Nigra to Basal Ganglia! Tuboinfindibular Pathway- Hypothalamus to the infindibular region.

15 Insular Cortex and Gustation! The insular cortex plays a major role in perceiving taste.! As the gustatory nerves (CN7, CN9 and CN10) enter the brain they move from the receptors on the tongue via the brain stem and medulla.! Once in the brain it enters the thalamus.! From the Thalamus axons branch out to three cortical structures: 1. The Insular Cortex (rostrodorsal cortex) 2. The Posterior limb of the Internal Capsule 3. The Operculum (primary gustatory cortex)! We believe that the Insular cortex is actively involved in the sense of taste and that is why your perception of a right eating time and mood makes you hungry or makes your food tastier.

16 Insula and the Operculum! The operculum is a covering layer that sheathes the junction under which the insula is found.! The operculum also houses the primary gustatory cortex which is responsible for taste perception.! The Operculum along with the Claustrum is credited with the protection of the Insular Cortex.! Bothe the Operculum and the PIC receive gustatory nerves as they exit the Thalamus and hence may both be linked.! Both regions are effected by dysphagia.! The sense of taste plays a vital role in higher level awareness.! The claustrum is credited multisensory integration (von economo neurons).

! There is speculation that the Anterior Insula is connected to the major swallowing regions including the primary motor cortex and the SMC.

17 Insula and Dysphagia! Dysphagia is a disease in which patients are found to have troubles in peristalsis (controlled by the vagus nerve)! In a study conducted, 3 out of 4 patients with isolated brain legions were diagnosed with Dysphagia.! There is speculation that the Anterior Insula is connected to the major swallowing regions including the primary motor cortex and the SMC.! This is one motor autonomic connection related to the insula.! The only patient who sis not report dysphagia had the lesion in the LPI and did not experience any motor or sensory deficits.! This may indicate the level of involvement and sophistication of the different lobes of the insula.

18 Insula and Thermoreception! The Anterior Insular Cortex has long been credited with the subjective sensation of temperature i.e. the relative feeling, I am feeling hot is sensed in the Anterior Insular Cortex. [5]! The thermosensory cortex is located on the dorsal margin left (collateral) insular cortex. This lobe is responsible for maintaining homeostasis in the brain. We will further elaborate on this in the Free Energy model slide.! This also references to be two by two cortex.! This subjective sense of temperature has been regarded as quintessential to both our consciousness and awareness.! These thermoreceptors have also been credited with the sensation of central pain

Possible correlations! Due to the diverse functions performed by the insular cortex we believe that there may be neural pathways connecting structures that have not yet been proven as connected.

19 Possible correlations! Due to the diverse functions performed by the insular cortex we believe that there may be neural pathways connecting structures that have not yet been proven as connected.! Both the AIC and the fusiform gyrus are highly activated when we remember faces.! dlpfc and AIC are involved in social interactions and impulsive decision making.! AIC and visual cortex are also effected when there are extremely short term sensations.! IC and Thalamus are both linked.

20 Schizophrenia (possible affects)! Recent studies have indicated theta the neurodegenerative disorder Schizophrenia has adverse effects on the Insular cortex. Other areas affected by the disease include the Amygadala, the primary auditory gyrus.! The fact that Schizophrenia affects all three could link the Insular cortex to more than just the sense of Sound.! Since Hallucinations, delusions and anxiety are effects of the disease, the insular cortex may also be linked to the two defects.! People also have not been able to think logically and act in unusual manners.

22 IC and Audition! The Posterior Insular cortex is actually believed to be well linked to the Auditory cortex in Humans.! The insulae are activated by passive listening and may thus participate in sound processing abstract knowledge about non-verbal is a motor and motor association area.! The insula is also activated when we listen to music and process melodic sounds or sense pain when we are subject to a harsh noise.! Since Temporal processing is integral to the sensation of sound, this ios also an indication of a connection between the Temporal lobe and the Insula which is more than just the Operculum.

23 Insular Cortex and Neurogenesis! Adult neurogenesis refers to the process by which neurons are created from progenitor cells to be integrated in neural circuits. The only known site for this fundamental activity is the subgranular zone of the hippocampal dentate gyrus [1].! Majority of the produced neurons are translocated by proteins and placed in either the cortical regions or the limbic brain.! Some of the neurons which find a path to the Limbic Brain also affect the Amygdala.! Since the Amydo-insular cortex link has been established it may be possible that the new neurons travel from the amygdala to the

24 IC and Cranial Nerves! We have already established a connection between several Cranial Nerves and the Insular cortex.! Cranial nerve 1 (Olfactory) runs through the insular cortex and differentiates between a pleasant and foul smell.! CN 8 (Auditory Vestibular) is also affected by Schizophrenia.! CN 10 (Vagus) is affected during dysphagia.! * Gustatory Nerves are also in use.! It also relays some spinal nerves as it houses some thermoreceptors.

25 Insula and Vision! The Top Down Axis of the Insula is meant to be related to visual sensation.! Visual awareness has been linked to insular cortex, the insular cortex is also credited with perceptual decision making.! We believe that there may be a connection between the V3 cortex (relays light signals) and the IC.! Further due to its involvement in empathy, we believe that it may have a connection to those structures which house mirror neurons i.e. the Fusiform Gyrus and the SMC! Lastly there may be a connection between the old visual pathway. The IC may just be connected to the superior colliculi.

26 IC and Parkinsons! Parkinsons is caused due to affected Dopamine pathway in the Basal Ganglia.! Majorly affects the D1 and D2 receptors.! These receptors are present on both the Insular Cortex and the Basal Ganglia.! The tremors caused due to Parkinsons may also strengthen a relation between the motor cortex and the Insula in a pathway where the role of the frontal lobe has been neglected.! Instability or loss of balance in the disease may be related to the connection of the Auditory Vestibular nerve or that of the Cerebellum.

IC and OCD! OCD is majorly caused due to hypoactivation of Serotonin Receptors and hence affects most seratonergic pathways.! It effects the decision making capacity of a person.

27 IC and OCD! OCD is majorly caused due to hypoactivation of Serotonin Receptors and hence affects most seratonergic pathways.! It effects the decision making capacity of a person.! Affects the functioning of the Motor Cortex as it forces people to act without thinking.! It may just effect the firing of Von Economo neurons.! The ACC is also adversely activated in OCD! SMC loses most activation in this disease.

28 Independent Lesioning! Induced Lesions were isolated to the Insular cortex and the effects were tested in four pateints.! All patients had different lobes of the insula lesioned! Other effects include damage to CN 7 and Anosognosia.! All four patients complained of speech problems including Dysphonia, Dysartheria and Cortical Stuttering.! This draws a direct link between the submandibular and sublingual glands.! The Insula may play an integral role in speech.! When one finds it difficult to swallow a fact or truth the insula may be part of the circuit.! Links back to the Brain Gut axis.! There was also problems in taste perception of the patients.

29 Mysteries of the IC! The Insular cortex is thick on the cortices and thin on the middle.! The activation of the IC in several neuropsychotic disorders.! IC connections via von economo neurons and their mapping.! Connection between the thalamus and the insula.! Lesioning of the insula why is it so rare.

31 Bibliography! [1] Aimone, James B., Fred H. Gage, and Sebastian Jessberger. "Adult Neurogenesis." - Scholarpedia. N.p., Web. 24 July 2015.! [2] "Mapping Brain Circuits Provides Clues to Schizophrenia, Earlier Detection of Psychosis." NIMH RSS. N.p., n.d. Web. 24 July 2015.! [3] "The Four Dopamine Pathways Relevant to Antipsychotics Pharmacology."- Psychopharmacology Institute. N.p., n.d. Web. 24 July 2015.! [4] [5] "Result Filters." National Center for Biotechnology Information. U.S. National Library of Medicine, n.d. Web. 27 July 2015.! [6] Medford, Nick, and Hugo D. Critchley. "Conjoint Activity of Anterior Insular and Anterior Cingulate Cortex: Awareness and Response." Brain Structure & Function. Springer-Verlag, n.d. Web. 28 July 2015.! [7] Craig, A. D. "Result Filters." National Center for Biotechnology Information. U.S. National Library of Medicine, n.d. Web. 28 July 2015.

32 ! [8] "Field Theories of Consciousness." - Scholarpedia. N.p., n.d. Web. 28 July 2015.! [9] "Researchers Identify Area Of The Brain That Processes Empathy - The Mount Sinai Hospital." The Mount Sinai Hospital. N.p., n.d. Web. 28 July 2015.! [10] "Brain." Anterior Insular Cortex Is Necessary for Empathetic Pain Perception. N.p., n.d. Web. 28 July 2015.! [11] "Neurosurgery." Search Results :. N.p., n.d. Web. 28 July 2015.! [12] "The Von Economo Neurons in the Frontoinsular and Anterior Cingulate Cortex." - Allman. N.p., n.d. Web. 28 July 2015.! [13] "The Effects of Schizophrenia on the Brain." The Effects of Schizophrenia on the Brain. N.p., n.d. Web. 28 July 2015.! [14] "Mapping Brain Circuits Provides Clues to Schizophrenia, Earlier Detection of Psychosis." NIMH RSS. N.p., n.d. Web. 28 July 2015.

33 ! [15] Blakeslee, Sandra. "A Small Part of the Brain, and Its Profound Effects." The New York Times. The New York Times, 05 Feb Web. 28 July 2015.! [16] "Cerebral Cortex." The Morphology of Supragranular Pyramidal Neurons in the Human Insular Cortex: A Quantitative Golgi Study. N.p., n.d. Web. 28 July 2015.

34 Special thanks to Shanaz, Jesse and Mom Jon Hardin Ishaan Kapoor Jun Won Hwang Sumil Nair

CEREBRUM & CEREBRAL CORTEX

CEREBRUM & CEREBRAL CORTEX Seonghan Kim Dept. of Anatomy Inje University, College of Medicine THE BRAIN ANATOMICAL REGIONS A. Cerebrum B. Diencephalon Thalamus Hypothalamus C. Brain Stem Midbrain Pons