Week 7 — Neural Correlates + Memory Part 1

What is the difference between a conscious state and conscious contents?

Conscious state = whether a person is capable of conscious experience at all. Conscious contents = what the person is experiencing at a particular moment (a voice, a face, pain, an internal thought).

What is a neural correlate of consciousness, and what two kinds of comparison do researchers use to find one?

A neural correlate is an event in the nervous system that occurs at the same time as, and may be the biological basis of, a specific mental event or state. Researchers compare different states (e.g., wakefulness vs. deep sleep) and different experiences (e.g., aware vs. unaware of a stimulus).

A researcher wants millisecond-by-millisecond timing of processing, and another wants to localise where activity differs. Which methods fit each goal, and why is brain stimulation different?

EEG and MEG suit timing (sequence of processing steps; MEG also gives better spatial resolution). fMRI suits localisation (where in a circuit activity differs). Brain stimulation (e.g., TMS) tests causality by perturbing the system, whereas fMRI activation alone is correlational.

Which brain systems support arousal, and which support awareness?

Arousal: brainstem and hypothalamic systems regulating wakefulness, interacting with the thalamus and basal forebrain to support cortical activation. Awareness: distributed cortical and thalamocortical activity, including a frontal-parietal network, supporting conscious contents.

What role does the locus coeruleus play in arousal and perception, according to lecture?

It is a brainstem nucleus that releases norepinephrine widely in the brain and enhances perceptual processing wherever attention is directed - described as a hot spot for attended processing.

Why is there no single consciousness centre in the brain?

Consciousness depends on interacting systems: damage to one critical structure, or damage to the connections between areas so they no longer communicate effectively, can each disrupt it.

A patient shows neither wakefulness nor any behavioural evidence of awareness, and EEG shows no sleep-wake cycle. Which disorder of consciousness is this?

Coma - the most severe condition in the lecture table: wakefulness absent, behavioural evidence of awareness absent.

A patient shows a sleep-wake cycle on EEG but no behavioural evidence of awareness on examination. Which condition is this, and what was it formerly called?

Unresponsive wakefulness syndrome, formerly called vegetative state: wakefulness present, behavioural evidence of awareness absent on examination.

A patient is awake and shows definite but limited and often inconsistent signs of awareness. Which condition is this, and how does it differ from unresponsive wakefulness syndrome?

Minimally conscious state. Unlike unresponsive wakefulness syndrome, it shows definite (though limited and inconsistent) comprehension/awareness, not merely wakefulness.

A patient is awake and aware but almost completely unable to move or communicate. Which condition is this, and why can it be mistaken for unconsciousness?

Locked-in syndrome: awareness is preserved, but severe restriction of movement makes awareness difficult to detect behaviourally.

What does the Terri Schiavo case illustrate about assessing consciousness?

The difficulty of the assessment: after a brain injury at age 26 in 1990, her husband requested termination of life support after 10 years while her parents wanted it continued, believing she reacted to them. Medical tests showed most of her brain was destroyed and doctors agreed she could not possibly have been conscious; her feeding tube was removed in 2005 and she died.

What does the Glasgow Coma Scale (GCS) assess, and what did the GCS-P add in 2018?

Clinicians systematically assess observable responses in three categories: eye-opening response, verbal response, and motor response. GCS-P, introduced in 2018, adds pupil reactivity.

Why is a failure to respond on a behavioural scale NOT proof that a patient lacks consciousness?

A failure to respond can reflect impaired movement, comprehension, or sensation instead of impaired awareness - so a behavioural scale is an imperfect measure of consciousness.

In Owen et al. (2006), an unresponsive patient was asked to imagine playing tennis and to imagine moving through their home. What brain activity was found, and what did it show? [Figure: owen-2006-tennis-spatial-navigation.png]

Tennis imagery activated the supplementary motor area (SMA); spatial-navigation imagery activated the parahippocampal place area (PPA) plus PMC/PPC - matching healthy controls. Despite unresponsive wakefulness, the patient understood spoken commands and responded through appropriate brain activity: covert command-following.

What is the default mode network (DMN), and what four kinds of internally directed cognition is it commonly involved in?

A large-scale network active when attention turns inward (e.g., mind-wandering, tuning out the outside world): self-referential thinking, autobiographical memory, imagining future events, and thinking about oneself and others (social cognition).

Name the DMN regions labelled in the lecture brain diagram. [Figure: dmn-brain-regions.png]

Posterior inferior parietal region, precuneus, posterior cingulate cortex, medial prefrontal cortex, and lateral temporal cortex.

What does functional connectivity mean, and what did Giacino et al. (2014) find for DMN connectivity across levels of consciousness? [Figure: dmn-connectivity-giacino-2014.png]

Functional connectivity is a statistical relationship: how strongly activity in different regions varies together, not proof of a direct connection. DMN connectivity was highest in healthy controls and declined with decreasing level of consciousness across minimally conscious, vegetative (unresponsive wakefulness), and coma groups, in PCC/precuneus, medial prefrontal cortex, temporoparietal junction, and parahippocampal gyrus.

In the Giacino et al. (2014) DMN graph, one blue dot sits at control-level connectivity. Whose data is it, and why does it matter?

A patient with locked-in syndrome. Even though they could not express awareness behaviourally, their DMN connectivity matched neurologically healthy controls - evidence of preserved consciousness despite paralysis.

During deep non-REM sleep, coma, unresponsive wakefulness, and general anaesthesia, what happens to communication among cortical regions?

Some forms of communication among cortical regions are reduced, and frontal-parietal communication is disrupted. The brain does not simply become inactive; the organisation of its activity is disrupted.

What is the central proposal of Global Neuronal Workspace Theory?

Specialised systems process information locally, but some information is amplified and shared widely (broadcast / ignition: a rapid, non-linear change in distributed activity). This global availability supports conscious access, via long-range interactions including the frontal-parietal network.

Global availability in the workspace supports three flexible uses. Name them, with the lecture's person-round-the-corner example.

Working memory: holding an object/idea in mind after the stimulus is removed (keeping the person in mind after they disappear round the corner). Generativity/creativity: reflecting on relationships or combinations among inputs (connecting seeing them with remembering you must tell them something). Flexibility: adjusting processing in one system in light of other systems (changing your goal/plan and following them).

What is the central proposal of higher-order theories of consciousness?

A sensory representation becomes conscious when the system also represents itself as being in that state. First-order representation: A red object is present. Higher-order representation: I am seeing a red object. The higher-order representation need not be deliberate or verbal.

How does higher-order theory explain blindsight, and what question does it raise?

A blindsight patient retains a first-order representation sufficient to guide visual judgments but lacks the higher-order representation that would support awareness. This raises: can sensory information guide behaviour without the representation needed for conscious experience?

What is the central proposal of Recurrent Processing Theory, and how does it differ from the workspace account on timing?

Feedforward processing - an initial pass through sensory pathways - can support processing without awareness. Recurrent processing - feedback interactions within and between sensory areas - supports conscious perception. Unlike the workspace account, conscious sensory experience may occur BEFORE information becomes globally available for report.

What is the central proposal of Integrated Information Theory (IIT), and what does it predict about feedback and differentiation?

Consciousness is integrated information: a system is conscious when its information is both highly differentiated (many distinct states) and highly integrated (the whole cannot be reduced to independent parts). Feedback loops support integration, so consciousness arises from causal structure (often quantified as phi), not merely from activity levels.

According to IIT, why are deep sleep and general anaesthesia unconscious?

Because differentiated, integrated activity - or feedback between regions - is reduced, so phi is low, even though the brain remains active.

A patient with a lesion of one cortical region loses a specific aspect of perception but remains aware of other aspects. What does this suggest about the neural basis of conscious contents?

A lesion can selectively remove a conscious content - a specific sensory property - while leaving other conscious experience intact.

What is the role of the frontoparietal network in visual awareness, and what happens if it is disrupted?

It is active when a stimulus is reported as seen, and is especially involved in monitoring, broadcasting, and reporting perceptual contents. Damage can impair awareness of visual contents even when sensory processing remains.

What is the role of the visual cortex in visual awareness, and what happens if it is damaged?

Early visual areas provide the detailed sensory representations that become the contents of visual experience. Damage can remove the corresponding content from experience (for example, visual field loss after V1 damage).

What is the distinction between the neural prerequisites of consciousness and the neural correlates of consciousness?

Neural prerequisites are conditions that make consciousness possible - for example, arousal, functioning sensory pathways, and basic cortical responsiveness - but do not themselves constitute conscious experience. Neural correlates are the specific patterns of activity associated with a given conscious content or state.

What is the distinction between the neural consequences of consciousness and the neural correlates of consciousness?

Neural consequences are processes that follow from conscious experience - for example, memory encoding of what was experienced, or behavioural responses to it - rather than the activity that constitutes the experience itself.

What is the hard problem of consciousness, and what question does it raise about neural correlates?

The hard problem asks why physical brain activity gives rise to subjective experience at all - the qualitative feel of experience. It raises: how do neural correlates explain why a conscious content feels like something?

What is a core challenge of measuring consciousness in patients who cannot communicate?

A lack of overt response does not prove absence of experience: patients may be conscious but unable to move, speak, or follow commands.

Why might a patient show no response in one test but respond in another?

Different tests tap different systems: for example, a patient may fail a motor-response task but succeed on a neuroimaging task that bypasses movement.

What is the key distinction between explicit memory and implicit memory?

Explicit memory: conscious recall/recognition of a prior event, with awareness that the memory refers to the past. Implicit memory: improved performance or a behavioural effect of a prior event without conscious recollection of that event.

What is the distinction between episodic memory and semantic memory, and which broader category do they belong to?

Episodic memory: memory for personally experienced events tied to time and place (episodes). Semantic memory: memory for general facts/concepts not tied to a personal event. Both are forms of explicit (declarative) memory.

What is the distinction between procedural memory and priming, and which broader category do they belong to?

Procedural memory: memory for skills/procedures (how to do things). Priming: exposure to one stimulus influences the response to a later stimulus, without conscious recollection. Both are forms of implicit (non-declarative) memory.

How does explicit memory change across the lifespan, according to lecture?

It improves through early life into adulthood and declines in later life, partly due to reduced processing speed and a reduction in the hippocampus.

How does implicit memory change across the lifespan, according to lecture?

It develops very early and remains relatively stable, with smaller lifespan changes than explicit memory - even though evidence is less consistent across task types.

A person gets much better at a task with practice but cannot say what they did or that they practised before. Which kind of memory is shown?

Implicit memory (for example, procedural memory for the skill), with a dissociation from explicit memory.

What is the distinction between encoding and retrieval?

Encoding: the process by which information is initially processed and stored. Retrieval: the process of recovering stored information.

Why is a failure to retrieve information not necessarily a failure to have encoded it, and what is a failure of encoding itself?

A retrieval failure means stored information cannot be accessed (for example, poor cues or interference) despite successful encoding. A failure of encoding means the information was never stored in the first place.

What is the role of the medial temporal lobe in memory?

It supports the initial formation of new memories - the encoding stage - rather than long-term storage itself.

What is the role of the neocortex in memory?

It is the main site of long-term storage, with memories distributed across sensory and association areas.

What is the role of the hippocampus in memory?

It encodes episodic memories, particularly for space and context, and supports consolidation over time.

What is the role of the basal ganglia in memory?

They support procedural learning - learning skills, habits, and sequences through practice.

What is the role of the cerebellum in memory?

It supports fine-tuning of motor skills and conditioned responses, especially precise timing and coordination.

In Cohen and Squire (1980), mirror reading was learned across three sessions, while participants did NOT learn a new reading rule each session. What does the graph show? [Figure: mirror-reading-cohen-squire-1980.png]

Mirror-reading time decreased steadily across sessions (learning retained across sessions). The new reversed passage read each session was consistently slower, showing that the improvement was not a general reading-rule gain but specific procedural learning of the repeated task.

Why does the Cohen and Squire mirror-reading study matter for memory theory? [Figure: mirror-reading-cohen-squire-1980.png]

It shows a dissociation: performance improves across sessions (implicit/procedural learning) even though the general reading rule is not learned afresh each session - evidence that implicit and explicit systems can operate independently.

What is the Atkinson-Shiffrin model, and what is its main limitation?

A modal model: sensory input enters sensory memory, is passed to short-term memory/working memory, and, if rehearsed, is transferred to long-term memory. Its main limitation is that it treats memory as a single pipeline, ignoring distinct systems for explicit and implicit memory and evidence that storage and retrieval are interactive.

What is the priming effect in word completion, and what does it show about implicit memory? [Figure: priming-word-completion.png]

People complete word stems (for example, _ _ _) with previously seen words more often than chance, even when they do not consciously recall the study list. This shows that prior exposure influences later performance without explicit recollection - a form of implicit memory.

What is the difference between recall and recognition, and which is typically easier?

Recall: retrieving information without cues (generating the answer). Recognition: identifying previously encountered information from presented options. Recognition is typically easier because cues support retrieval.

What is the key difference between free recall and cued recall?

Free recall: retrieving items with no cues. Cued recall: retrieving items with a prompt or hint that aids retrieval.

What does it mean to say memory is reconstructive?

Retrieval is not a perfect replay of a stored event: recalled memories are reconstructed at retrieval, influenced by current knowledge, expectations, and cues, so they can be distorted or altered.

What does it mean to say memory is a reconstructive process, and what evidence supports this?

Memories are not retrieved like a recording; they are rebuilt from stored fragments and current context, so errors and distortions can occur. For example, people often misremember details of events after misleading information or repeated questioning.

A patient remembers the specific word triads from a previous session AND reads new mirror-reversed triads faster with practice. Which memory systems are intact, and which are dissociated?

Both explicit memory (for the specific triads from the previous session) and implicit/procedural memory (faster mirror-reading with practice) are intact. The dissociation is that these systems can operate independently: explicit recall of prior items and implicit skill learning are not the same process.