Key Cognitive Disorders

Why This Matters

Cognitive disorders sit at the intersection of everything you'll study in cognitive psychology: attention, memory, executive function, perception, and emotion regulation. When these systems break down, we gain powerful insights into how they normally work. You're being tested not just on symptom lists, but on understanding which cognitive processes are disrupted and why specific treatments target those mechanisms. These disorders also show how biological substrates (neurotransmitters, brain structures) interact with cognitive functions to produce behavior.

Think of each disorder as a natural experiment revealing how the mind works. Alzheimer's teaches us about memory consolidation; ADHD illuminates attentional control; schizophrenia shows what happens when reality monitoring fails. Don't just memorize diagnostic criteria. Know what cognitive mechanism each disorder disrupts and how that explains the symptoms you observe.

---

Neurodegenerative Disorders

These conditions involve progressive deterioration of brain tissue, leading to cumulative cognitive decline. The key mechanism is neuronal death and the disruption of neural networks that support memory, reasoning, and daily functioning.

Alzheimer's Disease

• Progressive memory loss beginning with recent events. The hippocampus is affected early, which is why patients retain distant memories longer than new ones. This maps directly onto the consolidation process: older memories have already been transferred to cortical storage, but new memories can't complete that transfer.
• Amyloid plaques and tau tangles accumulate in brain tissue, disrupting synaptic communication and eventually causing neuronal death. These are the two hallmark pathological markers you need to know.
• No cure exists, but cholinesterase inhibitors (like donepezil) can temporarily slow symptom progression by boosting acetylcholine levels in remaining neurons. The cholinergic system is critical for memory encoding, so this treatment targets the specific neurotransmitter deficit.

Dementia

• An umbrella term for severe cognitive decline, not a single disease. Alzheimer's accounts for 60-80% of cases, but vascular dementia (caused by reduced blood flow to the brain) and Lewy body dementia (involving abnormal protein deposits) have distinct mechanisms.
• Core deficits span multiple domains: memory, language, executive function, and visuospatial processing, depending on which brain regions are affected.
• Risk factors include age, genetics, and modifiable lifestyle factors. Cardiovascular health, cognitive engagement, and social connection may offer some protection against onset or progression.

---

Neurodevelopmental Disorders

These conditions emerge during brain development, typically manifesting in childhood. They reflect atypical neural wiring that affects how individuals process information, regulate attention, and navigate social environments.

Attention Deficit Hyperactivity Disorder (ADHD)

• Impaired executive function is the core cognitive deficit, specifically in sustained attention, impulse control, and working memory. These deficits are linked to prefrontal cortex underactivity. The prefrontal cortex normally acts as the brain's "control center" for planning and self-regulation, so reduced activity there explains why these functions suffer.
• Dopamine dysregulation explains why stimulant medications (which increase dopamine availability) paradoxically calm hyperactive symptoms. Stimulants aren't adding energy; they're boosting the prefrontal cortex's ability to regulate behavior.
• Persists into adulthood in approximately 60% of cases, though hyperactivity often decreases while inattention and executive dysfunction remain.

Autism Spectrum Disorder

• Challenges in social cognition and communication, often linked to differences in theory of mind: the ability to infer others' mental states, intentions, and perspectives. This isn't about intelligence; it's about a specific cognitive process for modeling what other people think and feel.
• The "spectrum" designation reflects enormous variability, from individuals requiring substantial support to those with exceptional abilities in specific domains.
• Early intervention dramatically improves outcomes, particularly therapies targeting social skills, communication, and adaptive behavior during critical developmental windows when neural plasticity is highest.

---

Mood Disorders

These conditions primarily disrupt emotional regulation, but they significantly impair cognitive functions like concentration, memory encoding, and decision-making. The cognitive symptoms often persist even when mood improves, which tells us these aren't just "feeling sad" or "feeling up."

Depression

• Persistent low mood combined with cognitive deficits. Patients show impaired concentration, slowed processing speed, and negative memory bias, meaning they recall negative events more readily than positive or neutral ones. This bias helps explain why depression is self-reinforcing: the cognitive system keeps surfacing evidence that the world is bleak.
• Neurotransmitter imbalances in serotonin, norepinephrine, and dopamine systems underlie both emotional and cognitive symptoms. SSRIs (selective serotonin reuptake inhibitors) target the serotonin component specifically.
• High comorbidity with other disorders complicates both diagnosis and treatment. Depression frequently co-occurs with anxiety, PTSD, and chronic medical conditions.

Bipolar Disorder

• Alternating manic and depressive episodes create distinct cognitive profiles. Mania involves racing thoughts, impaired judgment, and distractibility; depressive episodes mirror unipolar depression's cognitive slowing and negative bias.
• Mood stabilizers like lithium work partly by modulating neurotransmitter systems and protecting against neuronal damage during episodes.
• Executive function deficits persist between episodes, even when mood is stable. This suggests the disorder involves ongoing cognitive vulnerability, not just mood dysregulation. That's an important distinction for exams.

---

Anxiety-Related Disorders

These conditions involve hyperactive threat-detection systems, leading to excessive fear responses and cognitive patterns like rumination, hypervigilance, and avoidance. Attention becomes biased toward perceived threats rather than being allocated flexibly.

Anxiety Disorders

• Attentional bias toward threat is the central cognitive feature. Anxious individuals show faster detection of threatening stimuli and difficulty disengaging attention from potential dangers. In lab tasks, they're quicker to spot an angry face in a crowd but slower to redirect focus afterward.
• Multiple subtypes exist: generalized anxiety disorder (chronic, diffuse worry across many domains), panic disorder (sudden intense fear with physical symptoms), and social anxiety disorder (fear of negative evaluation by others). Each has distinct cognitive patterns, but all share the threat-bias mechanism.
• Cognitive-behavioral therapy (CBT) effectively treats anxiety by restructuring maladaptive thought patterns and reducing avoidance behaviors through gradual exposure.

Obsessive-Compulsive Disorder (OCD)

• Intrusive obsessions trigger compulsive rituals. The cognitive mechanism involves impaired inhibition and an inflated sense of responsibility for preventing harm. For example, someone might know the door is locked but feel unable to suppress the thought that it isn't, leading to repeated checking.
• Exposure and response prevention (ERP) is the gold-standard treatment. It works by breaking the reinforcement cycle: the person faces the obsession trigger without performing the compulsion, and over time the anxiety response weakens (this is extinction learning in action).
• Neuroimaging reveals hyperactivity in the orbitofrontal cortex and anterior cingulate cortex, brain regions involved in error detection and behavioral monitoring. The brain is essentially stuck in a loop of detecting "errors" that aren't real.

Post-Traumatic Stress Disorder (PTSD)

• Trauma memories become fragmented and intrusive. The amygdala's fear response overwhelms hippocampal processing during the traumatic event, preventing proper memory consolidation. The result is a memory that's emotionally vivid but poorly organized in time and context.
• Flashbacks represent involuntary memory retrieval triggered by sensory cues (a sound, a smell, a visual scene). This demonstrates how emotional memories can bypass normal conscious recall and feel as though the event is happening again right now.
• Trauma-focused therapies like EMDR and prolonged exposure help by reprocessing traumatic memories, essentially giving the hippocampus a second chance to properly consolidate and contextualize the memory, reducing its emotional intensity.

---

Psychotic Disorders

Psychosis involves a fundamental break from shared reality, with disruptions in perception, belief formation, and thought organization. These conditions reveal how the brain normally constructs and monitors our experience of reality.

Schizophrenia

Schizophrenia's symptoms are divided into two categories, and understanding this split is essential for exams.

• Positive symptoms add experiences that shouldn't be there: hallucinations (perceiving stimuli that don't exist, most commonly auditory) and delusions (fixed false beliefs resistant to contradictory evidence). These reflect failures in reality monitoring and source attribution, meaning the brain can't distinguish internally generated thoughts from external input.
• Negative symptoms subtract normal function: flat affect, social withdrawal, and reduced motivation. These suggest disrupted reward processing and executive function, and they tend to be harder to treat than positive symptoms.
• The dopamine hypothesis remains central. Antipsychotic medications work primarily by blocking $D_2$ dopamine receptors, reducing positive symptoms. However, glutamate and serotonin systems are also implicated, and newer research points to a more complex neurochemical picture.

---

Quick Reference Table

---

Self-Check Questions

1. Both Alzheimer's disease and depression can cause memory problems. How do the underlying mechanisms differ, and how would you distinguish them clinically?

2. Which two disorders involve disrupted executive function as a core feature, and what specific executive processes are impaired in each?

3. Compare and contrast the attentional biases seen in ADHD versus anxiety disorders. How does attention malfunction differently in each condition?

4. If an FRQ asks you to explain how cognitive-behavioral therapy works, which disorders would provide the best examples, and what cognitive mechanisms does CBT target?

5. Schizophrenia and bipolar disorder can both involve psychotic symptoms. What key difference in the timing and context of psychosis distinguishes these two disorders?