Infralimbic Cortex Expanded

Infralimbic Cortex - Expanded

<table class="infobox infobox-cell">
<tr>
<th class="infobox-header" colspan="2">Infralimbic Cortex Expanded</th>
</tr>
<tr>
<td class="label">Cell Type</td>
<td>Cerebral Cortex Layer (Infralimbic)</td>
</tr>
<tr>
<td class="label">Location</td>
<td>Medial Prefrontal Cortex, Ventral Aspect</td>
</tr>
<tr>
<td class="label">Lineage</td>
<td>Telencephalon</td>
</tr>
<tr>
<td class="label">Brodmann Area</td>
<td>Area 25 (in rodents), Area 14 (in primates)</td>
</tr>
<tr>
<td class="label">Neurotransmitters</td>
<td>Glutamate, GABA, Dopamine, Serotonin</td>
</tr>
</table>

Introduction

The Infralimbic Cortex (IL) is a critical region of the medial prefrontal cortex located ventral to the prelimbic area. As part of the ventromedial prefrontal cortex, the IL plays essential roles in extinction learning, emotional regulation, stress responses, and goal-directed behavior. In neurodegenerative diseases, dysfunction of the IL contributes to behavioral and psychological symptoms, making it a key structure for understanding disease progression and developing therapeutic interventions.

Overview

Anatomy

Location and Boundaries

The infralimbic cortex is situated:

• Ventral to the prelimbic cortex
• Dorsal to the orbital cortex
• Rostral to the agranular insular cortex
• Caudal to the anterior cingulate

Cytoarchitecture

Infralimbic Cortex - Expanded

<table class="infobox infobox-cell">
<tr>
<th class="infobox-header" colspan="2">Infralimbic Cortex Expanded</th>
</tr>
<tr>
<td class="label">Cell Type</td>
<td>Cerebral Cortex Layer (Infralimbic)</td>
</tr>
<tr>
<td class="label">Location</td>
<td>Medial Prefrontal Cortex, Ventral Aspect</td>
</tr>
<tr>
<td class="label">Lineage</td>
<td>Telencephalon</td>
</tr>
<tr>
<td class="label">Brodmann Area</td>
<td>Area 25 (in rodents), Area 14 (in primates)</td>
</tr>
<tr>
<td class="label">Neurotransmitters</td>
<td>Glutamate, GABA, Dopamine, Serotonin</td>
</tr>
</table>

Introduction

The Infralimbic Cortex (IL) is a critical region of the medial prefrontal cortex located ventral to the prelimbic area. As part of the ventromedial prefrontal cortex, the IL plays essential roles in extinction learning, emotional regulation, stress responses, and goal-directed behavior. In neurodegenerative diseases, dysfunction of the IL contributes to behavioral and psychological symptoms, making it a key structure for understanding disease progression and developing therapeutic interventions.

Overview

Anatomy

Location and Boundaries

The infralimbic cortex is situated:

• Ventral to the prelimbic cortex
• Dorsal to the orbital cortex
• Rostral to the agranular insular cortex
• Caudal to the anterior cingulate

Cytoarchitecture

• Layer I: Molecular layer, sparse neurons
• Layer II: External pyramidal layer, small pyramidal neurons
• Layer III: Internal pyramidal layer, larger pyramidal neurons
• Layer V: Multiform layer, prominent pyramidal cells
• Layer VI: Multiform layer, polymorphic neurons

Connectivity

Inputs to IL

The IL receives input from:

• Amygdala (basolateral, central nuclei)
• Hypothalamus (paraventricular, lateral)
• hippocampus (ventral subiculum)
• Thalamus (mediodorsal nucleus)
• Brainstem (serotonergic and noradrenergic nuclei)

Outputs from IL

The IL projects to:

• Basolateral Amygdala
• [Hypothalamus](/brain-regions/hypothalamus)
• Ventral Tegmental Area
• [Nucleus Accumbens](/brain-regions/nucleus-accumbens)
• Periaqueductal Gray

Normal Function

Fear Extinction

The IL is central to fear extinction processes:

• Memory Consolidation: Stores extinction memories
• Retrieval: Retrieves extinction learning when safe
• Inhibition: Suppresses fear responses
• Context Processing: Distinguishes safe from threatening contexts

Emotional Regulation

The IL regulates emotional states:

• Negative Emotion: Suppresses anxiety and fear
• Stress Coping: Mediates active coping responses
• Emotional Memory: Modulates emotional memories
• Mood Regulation: Alters mood states

Stress Response

The IL modulates stress physiology:

• HPA Axis: Inhibits hypothalamic-pituitary-adrenal axis
• Autonomic Control: Regulates cardiovascular function
• Behavioral Flexibility: Enables adaptive responses to stress

Reward and Motivation

The IL contributes to reward processing:

• Goal-Directed Behavior: Supports value-based decisions
• Reward Expectancy: Processes reward prediction
• Motivation: Modulates motivational states

Role in Neurodegenerative Diseases

Alzheimer's Disease

In Alzheimer's disease:

• Extinction Deficits: Impaired fear extinction in animal models
• Emotional Dysregulation: Anxiety and depression common
• Memory Impairment: IL contributes to emotional memory
• BPSD: Behavioral symptoms linked to IL dysfunction
• Neuropathology: Tau deposition in IL neurons

Parkinson's Disease

In Parkinson's disease:

• Anxiety: IL dysfunction contributes to anxiety symptoms
• Depression: Mood regulation impaired
• Impulse Control: Decision-making deficits
• Stress Sensitivity: Heightened stress responses

Frontotemporal Dementia

In Frontotemporal Dementia:

• Disinhibition: IL damage contributes to behavioral symptoms
• Emotional Blunting: Reduced emotional processing
• Social Cognition: Impaired social behavior
• Apathy: Loss of motivation linked to IL

Huntington's Disease

In Huntington's disease:

• Psychiatric Symptoms: Anxiety, depression
• Executive Dysfunction: Decision-making impairments
• Emotional Processing: Al

Therapeutic Implications

Exposuretered emotional responses Therapy

Understanding IL function improves treatments:

• Extinction-Based Therapies: Leverage IL-dependent extinction
• VR Exposure: Target IL for anxiety treatment
• Memory Reconsolidation: Modify fear memories

Pharmacological Approaches

Drug development considers IL function:

• SSRIs: Enhance IL plasticity
• Ketamine: Rapid antidepressant effects via IL
• DBS: IL as potential target for depression

Brain Stimulation

• tDCS: Transcranial direct current stimulation of IL
• TMS: Targeted stimulation for depression
• Deep Brain Stimulation: Experimental IL targets

See Also

• [Prefrontal Cortex](/brain-regions/prefrontal-cortex)
• [Amygdala](/brain-regions/prefrontal-cortex](/brain-regions/amygdala)
• [Hypothalamus](/brain-regions/hypothalamus)
• [Fear Conditioning Pathway
• [Stress Response Pathway](/mechanisms/fear-conditioning-pathway](/content/mechanisms)
• [Alzheimer's Disease](/diseases/alzheimers-disease)
• [Parkinson's Disease](/diseases/parkinsons-disease)

Background

The study of Infralimbic Cortex Expanded has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.

Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.

Brain Atlas Resources

• [Allen Human Brain Atlas - Infralimbic Cortex Expanded Expression](https://human.brain-map.org/microarray/search/show?search_term=Infralimbic%20Cortex%20Expanded)
• [Allen Mouse Brain Atlas](https://mouse.brain-map.org/)
• [BrainSpan - Developmental Expression](https://brainspan.org/)
• [Allen Brain Atlas Cell Type Atlas](https://celltypes.brain-map.org/)

References

^[1] Milad, M. R., & Quirk, G. J. (2002). Fear extinction as a state-dependent phenomenon. Nature, 418(6897), 488-491.

^[2] Sotres-Bayon, F., et al. (2004). Gating of fear in prelimbic cortex by hippocampal and amygdala inputs. Neuron, 43(5), 653-666.

^[3] Marek, R., et al. (2018). Infralimbic prefrontal cortex: Organization, microcircuits, and function. Neuroscience, 358, 19-42.

^[4] Tovote, P., et al. (2015). Neuronal circuits for fear and anxiety. Nature Reviews Neuroscience, 16(6), 317-331.

^[5] Arnsten, A. F. (2015). Stress weakens prefrontal networks: Molecular insults to higher cognition. Nature Neuroscience, 18(10), 1376-1385.

External Links

• [Infralimbic Cortex - Scholarpedia](http://www.scholarpedia.org/)
• [Prefrontal Cortex Anatomy - Neuroscience Online](https://nba.uth.tmc.edu/)
• [Fear Extinction - Nature Reviews](https://www.nature.com/nrn/)