Cumulative level test: Coordination, modulation and the human measurement problem: from coupled rhythms to the assessment of consciousness

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12 questions · 80% to pass · no timer. This longer test revisits both units in the level. These authored questions assess recognition and application of the taught distinctions, not professional qualification. You may review the lessons and retry. Repeat attempts reuse the question bank; a remembered answer is not proof of transfer to a new situation.

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Question 1

Hippocampal theta in a rat runs at 7 Hz while gamma runs at 60 Hz. During a spatial choice, gamma amplitude is greatest at the trough of theta. If the coupling is real, how many gamma cycles fit within one theta cycle, and what would a report that one gamma burst occurs per theta cycle imply about the coupling?About 8.6 gamma cycles fit in one 143 ms theta cycle, so a single gamma burst per theta cycle is a sparse, phase-specific relationship rather than continuous amplitude modulation, and the ratio should be reported with the phase of peak amplitude.About 2 gamma cycles fit in one theta cycle, so the coupling indicates that each theta cycle contains two independent gamma events.

Question 2

Participants perform a contrast discrimination task. Those with high pre-stimulus tonic pupil diameter show worse discrimination and larger response variability, while those with intermediate diameter perform best, and a phasic pupil response to the stimulus predicts faster correct responses. Which framework organises these results?Pupil diameter indexes effort, so the high-tonic group performed worse because they were trying harder and became distracted.An inverted-U relation in which tonic arousal sets the gain of cortical responding: intermediate tonic activity supports discrimination, high tonic activity increases variability and favours disengagement, and the phasic response reflects a transient gain increase to the stimulus.

Question 3

Rats receive selective immunotoxic lesions of basal forebrain cholinergic neurons and are tested on a five-choice serial reaction time task. They make more omission errors and have slower correct responses, but accuracy on trials they complete is unchanged, and performance falls further when the inter-trial interval is made variable. What is the best interpretation?The pattern points to a deficit in attentional capture and response readiness rather than in discrimination, because accuracy conditional on responding is spared while omissions and timing-dependent performance deteriorate.The lesion impaired memory, since the animals failed to complete trials and therefore could not remember the correct response.

Question 4

A drug that is a substrate of P-glycoprotein at the blood-brain barrier is given with a second drug that inhibits P-glycoprotein. Brain concentrations of the first drug rise tenfold while plasma concentrations rise only 1.3-fold. A commentary describes this as proof that the barrier is failing in patients with inflammation. What is wrong with the commentary?The tenfold rise in brain concentration shows that the barrier had already broken down, since a healthy barrier would exclude the drug entirely.The experiment shows that an efflux transporter was limiting brain entry, which is a normal regulated function of the barrier; calling it barrier failure confuses transporter inhibition with loss of tight-junction integrity.

Question 5

Patients receiving interferon-alpha for hepatitis C develop depression at a higher rate than controls, and pretreatment with an antidepressant reduces the incidence. A review concludes that inflammation causes depression. Which refinement is required?The trial supports a causal contribution of cytokine signalling to a depressive syndrome in a clinical population, but the effect is conditional on dose, vulnerability and treatment context, and it does not establish that inflammation is the cause of depression in general.Since blocking the effect pharmacologically prevented depression, inflammation is established as the cause of major depression.

Question 6

A human single-unit study records from the medial temporal lobe in 9 patients with epilepsy and reports neurons that respond selectively to images of the actress Jennifer Aniston. What can be concluded about the representation of familiar people in the human brain?The existence of a Jennifer Aniston neuron shows that the brain stores each familiar person in a single dedicated cell.The recordings establish that some human medial temporal neurons respond selectively to particular familiar individuals, which constrains theories of representation, but the sample is small, drawn from a clinical population, and cannot establish the format or the prevalence of such coding.

Question 7

A single patient with a rare lesion is scanned while viewing faces. The contrast of faces versus houses produces a strong left fusiform cluster. The authors publish it as a case study locating the face area. Colleagues note that repeating the scan in the same patient on a second day produces a cluster in a different location. What does this imply?The between-session instability shows that a single-subject map is not a reliable localiser, so the case can motivate a hypothesis but cannot establish the location of a function without a replication sample and a reliability estimate.The second scan failed because the patient was tired, so the first result stands as the valid localisation.

Question 8

One hertz repetitive transcranial magnetic stimulation over the left parietal cortex for 20 minutes reduces performance on a number comparison task for 15 minutes afterwards, while stimulation over the right parietal cortex and sham stimulation have no effect. A reviewer asks how many pulses were delivered and what the after-effect demonstrates.The protocol delivered 20 pulses, one per minute, and the after-effect demonstrates that the left parietal cortex stores numerical magnitude.The protocol delivered 1200 pulses (1 Hz for 1200 seconds), and the after-effect demonstrates that disrupting the left parietal region transiently impairs task performance, which is a necessity claim about a time-averaged contribution rather than about the specific computation.

Question 9

Intraoperative recordings from the subthalamic nucleus in Parkinson patients show that local field potential power in the beta band (13 to 30 Hz) falls when dopaminergic medication is given and when therapeutic stimulation is switched on, and that beta power correlates with rigidity scores. A paper concludes that beta oscillations cause parkinsonian rigidity. Which issue is most important?The correlation across states is consistent with beta activity as a marker or contributor, but causation requires manipulation of beta independently of medication and stimulation and a demonstration that rigidity follows the manipulation, because both interventions change many things at once.The fact that two independent interventions both reduce beta power and rigidity shows that beta is the common causal pathway.

Question 10

Under propofol sedation, a volunteer is unresponsive and has low perturbational complexity. Under ketamine, a volunteer is also unresponsive but has complexity values within the range seen in wakefulness, and reports vivid dreams afterwards. What does this dissociation imply for the use of complexity as a consciousness measure?It implies that ketamine does not actually produce unconsciousness, so the ketamine condition should be excluded from validation studies.It implies that complexity tracks the integrated capacity for conscious processing rather than behavioural responsiveness, and that unresponsiveness can coexist with a wake-like complexity and with reported experience, so the index must be interpreted with the drug and the state in mind.

Question 11

You want to test whether theta-gamma coupling in the human hippocampus is necessary for memory encoding. You have access to intracranial electrodes in epilepsy patients and to repetitive transcranial magnetic stimulation. Which design best supports a causal claim?Measure coupling during encoding with intracranial electrodes, then use stimulation time-locked to the theta phase to disrupt the gamma burst in a subset of trials, and test whether the disruption reduces coupling and subsequently reduces recall of those specific items.Stimulate the hippocampus at gamma frequency and show that recall improves, since improving memory demonstrates that the coupled rhythm is the mechanism.

Question 12

A team proposes to test whether locus coeruleus noradrenergic activity sharpens cortical orientation tuning in humans. They plan to use pupil diameter as the index of locus coeruleus activity, a 7-tesla scan to localise the nucleus, and a placebo-controlled beta blocker to manipulate noradrenergic signalling. Which limitation most needs to be addressed in the design?The design is sound because the three measures triangulate the same construct, and agreement among them would establish that noradrenaline sharpens tuning.All three measures are indirect and none is specific to the locus coeruleus: pupil diameter integrates multiple arousal pathways, the brainstem signal is contaminated by nearby vasculature and motion, and a systemic beta blocker acts at many receptors throughout the body and brain, so the design needs converging measures and a manipulation that can dissociate noradrenergic from general arousal.

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