Cognitive Neuroscience
Voluntary vs. Involuntary Attention
• Voluntary Attention: Controlled, intentional focus on a stimulus (top-down).
• Involuntary Attention: Automatic, stimulus-driven focus (bottom-up).
Visual Neglect
• Definition: A neurological condition where individuals fail to attend to stimuli on one side of space, often due to brain damage (e.g., to the right parietal lobe).
• Why a Disorder of Attention: Involves deficits in allocating attention rather than sensory impairments.
Posner Cueing Paradigm
• Focus: Measures how attention shifts due to cues.
• Facilitation: Faster responses to cued locations at short intervals.
• Inhibition of Return (IOR): Slower responses to previously cued locations at longer intervals.
ERP Responses as Indices of Selective Attention
• N1 and P1 Components: Larger amplitude for attended targets, reflecting early sensory selection in attention processing.
ERP Responses and Inhibition of Return (IOR)
• P1 Component: Enhanced for uncued trials at longer stimulus-onset asynchronies (SOAs), indicating IOR.
Source vs. Site of Attention Effects
• Source: Top-down mechanisms (e.g., executive control systems) that regulate attention.
• Site: The location or neural region where attention is focused.
Negative Priming (NP)
• Basic Paradigm: Slower response to a previously ignored stimulus when it becomes relevant.
• Theories of NP:
o Inhibition: Suppressed processing of ignored items.
o Episodic Retrieval: Conflict due to mismatch in previous and current stimulus relevance.
• Neural Basis: Involvement of specific brain regions like the prefrontal cortex (Enger & Hirsch, 2005).
• Implications for Schizophrenia: Deficits in NP may reflect impaired attention regulation (Unger et al., 2010)
Memory
Sensory Memory
• Definition: Brief retention of sensory information.
• Echoic Memory: Auditory sensory memory, lasting a few seconds.
• Sensory Store: The initial stage of memory that briefly holds all incoming sensory information.
Working Memory
• Definition: Active processing and storage of information for short-term use.
• Neural Basis:
o Verbal: Associated with Broca’s and left prefrontal regions.
o Nonverbal: Linked to the right prefrontal and parietal regions.
• N-back Task: A cognitive test requiring participants to identify if a stimulus matches one presented 'n' steps earlier; measures working memory capacity.
• Monitoring vs. Manipulating Information:
o Champod and Petrides (2010):
▪ Monitoring: Linked to the frontal regions.
▪ Manipulating: Linked to the frontal and parietal regions.
Long-Term Memory
• Semantic vs. Episodic Memory:
o Semantic: Facts and general knowledge.
o Episodic: Personal experiences and events.
• Explicit vs. Implicit Memory:
o Explicit: Conscious recall (e.g., facts).
o Implicit: Unconscious memory (e.g., skills).
o HM Case Study: Surgical removal of medial temporal lobes impaired explicit memory but preserved implicit memory, highlighting the distinction.
Neural Basis of Implicit Memory
• Weather Prediction Task: A probabilistic learning task demonstrating the role of the basal ganglia in implicit memory.
Encoding Paradigms
• Ranganath, Yonelinas, & D’Esposito (2004):
o Differentiated familiarity (vague recognition) and source recollection (specific memory of the context).
Alzheimer’s Dementia
• Symptoms: Memory loss, confusion, difficulty with daily tasks.
• Progression: From mild memory lapses to severe cognitive impairment.
• Risk Factors: Age, genetics (e.g., APOE-ε4), lifestyle.
• Pathology:
o Beta Amyloid: Protein plaques disrupting neuronal communication.
o Tau Tangles: Protein tangles damaging neuron structure.
• Role of PET and fMRI: Imaging tools to study amyloid deposition, brain atrophy, and progression of the disease.
Speech Perception
Neuroanatomy of the Auditory Cortex
• Key regions:
o Heschl’s gyrus and planum temporale.
o Associated with language dominance and laterality(e.g., left hemisphere in most people).
• Tonotopic organization:
o The auditory cortex is organized by frequency.
o Binaural input representation: Evidence of bilateral neural representation of sound from both ears; however, LH > Sound from Right Ear and vice versa
Mismatch Negativity (MMN) in Speech Perception
• MMN basics:
o Brain response to deviations in auditory stimuli.
o Paradigm involves comparing standard and deviant sounds.
• Language specificity studies:
o Näätänen et al., 1997: Finnish and Estonian participants showed MMN differences tied to native phoneme categories.
o Highlights the role of MMN in understanding:
▪ Language development.
▪ Second-language (L2) learning.
Neuroanatomy of Speech Processing
• Differentiation between:
o Speech without understanding (auditory processing without semantic interpretation).
o Semantic understanding of speech (involves higher-level cognitive and language processing).
Second Language (L2) Learning
Factors Impacting L2 Proficiency
• Study by Jakoby et al., 2011:
o Variations in L2 proficiency linked to:
▪ Neural differentiation of phoneme categories.
▪ MMN as a potential marker of phoneme discrimination abilities.
• Implications:
o Individual differences in neural plasticity and auditory processing affect L2 learning outcomes.
Reading
Reading for Meaning
Pathways in Reading
• Phonological pathway: O – P - S
o Involves decoding written text into sounds.
• Orthographic pathway: O - S
o Direct recognition of word forms without phonological decoding.
o Essential for fluent reading.
Homophone Error Paradigm
• Logic: Errors arise when phonologically identical words (homophones) are misinterpreted (e.g., "flour" vs "flower"), which is evidence for the phonological pathway
• ERP (Event-Related Potential) studies:
o Focus on N400 component:
o Used to understand time course of phonological activation during reading.
Neuroanatomy of Reading
• Inferior frontal gyrus:
o Phonological processing with emphasis on subvocal articulation.
• Temporo-parietal regions:
o Phonological processing at the whole word level.
o Integration with semantic processing.
• Occipitotemporal area:
o Houses the visual word form area (VWFA).
o Critical for recognizing written words and letter patterns.
Reading Disabilities
Developmental Dyslexia
• Key theories:
o Phonological Theory: Suggests a deficit in phonological awareness as the core issue in reading difficulties (e.g., developmental dyslexia).
o Magnocellular Theory: Proposes that reading disabilities are due to a deficit in the magnocellular system, which is involved in processing visual and auditory motion.
• Neurobiology:
o Comparison:
▪ No history of reading troubles: Efficient neural connections for reading.
▪ Developmental dyslexia: Disruptions in phonological and orthographic pathways.Reduced activation in the left frontal, temporoparietal and VWFA; compensatory activation in the right hemisphere
Diffusion Tensor Imaging (DTI)
• Focuses on white matter pathways:
o Integrity of connections impacts reading ability.
o Individuals with reading challenges often show reduced white matter integrity in key reading-related pathways.
Cognitive Control
Frontal Lobe Pathology
• Overview: Damage to the frontal lobes can result in impairments in cognitive, emotional, and social behaviors.
• Key Syndromes:
o Dorsolateral Syndrome:
▪ Symptoms: Poor planning, organization, and goal-directed behavior.
▪ Associated deficits: Working memory and cognitive flexibility.
o Orbitofrontal Syndrome:
▪ Symptoms: Disinhibition, impulsivity, socially inappropriate behavior.
▪ Associated deficits: Emotional regulation and decision-making.
Importance of the Frontal Lobes (Prefrontal Cortex)
• Central to cognitive control:
o The ability to regulate thoughts and actions in pursuit of goals.
• Key functions of the prefrontal cortex:
o Forming goals and objectives.
o Developing and sequencing plans to achieve those goals.
o Monitoring progress and making adjustments.
o Shifting gears (cognitive flexibility) when needed.
o Evaluating successes and failures for future adaptation
Cognitive Control
• Definition: The capacity to coordinate mental processes to achieve a specific objective.
• Daily Examples:
o Planning your day.
o Adapting when unexpected events disrupt plans.
o Tracking progress toward completing a project.
o Evaluating why a task succeeded or failed.
Clinical and Experimental Measures of Cognitive Control
Wisconsin Card Sorting Task (WCST):
o Tests cognitive flexibility and problem-solving.
o Patients must sort cards based on shifting rules, requiring them to adapt when the rules change.
o Deficits in performance (perseverating on an old rule)often linked to dorsolateral prefrontal cortex (DLPFC) damage.
fMRI Adaptations of WCST:
o Highlights the role of the DLPFC in:
▪ Rule maintenance.
▪ Working memory (WM) integration for cognitive control.
o Working Memory (WM):
▪ Critical for holding task-relevant information during problem-solving.
Task-Switching Paradigm:
o Evaluates the ability to shift between tasks or rules.
o Shows strong overlap between cognitive control and WM demands.