Introduction to the Neurobiology of Mental Disorders
(A concise, structured overview for study or review)
1. Core Concepts
| Concept |
Definition |
Relevance to Mental Disorders |
| Neurotransmission |
Release of chemical messengers (neurotransmitters) from a presynaptic neuron, binding to receptors on a postsynaptic cell, and termination of the signal. |
Imbalances in serotonin, dopamine, norepinephrine, GABA, and glutamate underlie many mood, anxiety, and psychotic disorders. |
| Neuroplasticity |
The brain’s ability to change its structure and function in response to experience, learning, or injury. |
Dysregulated plasticity can contribute to persistent maladaptive circuits (e.g., in depression or PTSD). |
| Neurocircuitry |
Networks of interconnected brain regions that process specific types of information (e.g., reward, fear, executive control). |
Specific circuit dysfunctions are linked to symptom clusters (e.g., hyperactive amygdala in anxiety). |
| Gene‑Environment Interaction (G×E) |
The interplay between genetic susceptibility and environmental exposures (stress, trauma, substance use). |
Explains why not all genetically “at‑risk” individuals develop a disorder and why environmental factors can trigger illness. |
2. Major Brain Systems Implicated in Psychiatric Illness
| System |
Key Structures |
Primary Functions |
Typical Dysfunctions in Disorders |
| Monoaminergic System |
Raphe nuclei (serotonin), Locus coeruleus (norepinephrine), Ventral tegmental area (dopamine) |
Mood regulation, arousal, reward, attention |
↓ Serotonin → depression, anxiety; ↑ Dopamine → psychosis; ↓ Norepinephrine → ADHD, depression |
| Limbic System |
Amygdala, Hippocampus, Ventral striatum |
Emotion processing, memory, reward |
Amygdala hyper‑reactivity → anxiety/PTSD; Hippocampal volume loss → depression, PTSD |
| Prefrontal Cortex (PFC) |
Dorsolateral PFC, Ventromedial PFC, Anterior cingulate |
Executive function, decision‑making, impulse control |
Hypofrontality → schizophrenia, ADHD; Dysregulated ventromedial PFC → mood disorders |
| Default Mode Network (DMN) |
Medial PFC, Posterior cingulate, Precuneus |
Self‑referential thought, mind‑wandering |
Hyperconnectivity → rumination in depression; hypoconnectivity → attentional deficits |
| Salience Network |
Anterior insula, Dorsal anterior cingulate |
Detects salient stimuli, switches between DMN & task‑positive networks |
Aberrant salience attribution → psychosis; altered switching → anxiety |
| HPA Axis (Neuroendocrine) |
Hypothalamus → Pituitary → Adrenal cortex |
Stress response, cortisol release |
Chronic hyper‑cortisol → hippocampal atrophy, mood dysregulation |
3. Neurotransmitter Systems & Representative Disorders
| Neurotransmitter |
Primary Receptors |
Pharmacologic Targets |
Representative Disorders |
| Serotonin (5‑HT) |
5‑HT1A, 5‑HT2A, 5‑HT3, etc. |
SSRIs, SNRIs, 5‑HT2A antagonists |
Major depressive disorder (MDD), OCD, anxiety disorders, some eating disorders |
| Dopamine |
D1‑ |
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