Primary Takeaways from the Readings

Question 1

Neurologic manifestations of major electrolyte abnormalities

Answer 1

(Diringer, 2017)

• ## We need precise electrolyte regulation (e.g., over their concentrations/gradients across cellular compartments)
• ## If these relationships are disturbed, here’s what happens:
• Alterations in extracellular fluid sodium concentrations = produces water shifts that lead to brain
  swelling or shrinkage. Usually can get back to normal, unless you correct too fast or overcorrect.
• Magnesium, phosphate, calcium = Issues with perception. Hypomagnesemia and hypocalcemia can lead to weakness, and muscle spasms. Hypophosphatemia and hypomagnesemia can impair respiratory function (via weakness).
• Seizures can be seen in cases of very low concentrations of all three.

Question 2

How does oxytocin modulate human behavior?

Answer 2

(Yao & Kendrick, 2024)

• Oxytocin can influence cognitive, emotional and social
  functions.
• It is still unclear how it acts - though it seems to primarily influence behavior indirectly through neuromodulatory interactions with classical transmitters and other peptides - which then themselves independently influence behavior,
• Oxytocin-based interventions have been trialed for ASD and schizophrenia - resulting in small improvements in social behaviours.
• Its most potent effects appear to be in increasing attention to socially-salient environmental cues (though the way in which this functions differs across sexes and contexts)
• It also modulates cognitive, emotional and reward processing - to promote interpersonal social understanding, attraction and bonds - and social group
  cohesion through increased conformity, altruistic punishment and moral emotions.
• OT also increases co-operation and protection across both social domains.

Question 3

Oxytocin—a social peptide? Deconstructing the evidence

Answer 3

(Leng et al., 2022)

• The claim that oxytocin is a social neuropeptide came from the observation that it is s instrumental in the
  initiation of maternal behaviour - which people then extended to claim that it promotes social behaviours between individuals.
• Having reviewed evidence from mechanistic studies in animals (understand the pathways of behavioural
  effects of centrally administered oxytocin), observational
  studies indicating an association between oxytocin signalling pathways and social behaviour, intervention studies in which oxytocin is typically administered intranasally, and translational studies of patients with disorders of social behaviour – and concluding that the evidence is weak!
• The narrative of a prosocial role for oxytocin attracted mainstream media interest.
• Despair at the lack of progression in treatment approaches for autism and schizophrenia also grew.
• The authors think this is a case of confirmation bias.
• Most of the evidence is associational or methodologically flawed - the authors argue that oxytocin exerts diverse effects on many peripheral tissues, so how can we be sure that any behavioural effects are not secondary to one of these?
  And, as oxytocin affects many different functions and
  behaviours, how can we be sure that what we are observing is a primary effect rather than an epiphenomenon (by-product, secondary effect)?

Question 4

Human Gender Development

Answer 4

(Hines, 2020)

• Gender is multi-dimensional, its causes are multi-faceted, and we are far from a full understanding of how gender-related characteristics develop.
• What we do know - prenatal and early neonatal testosterone (T) exposure and socialization influence gender development.
• Early testosterone influences gender role behavior (e.g., gender-typed object/toy preferences), gender identity and sexual orientation.
• Some have argued that it influences spatial skills (e.g., mental rotation) or autistic traits too - but the evidence for this is inconsistent.
• While early testosterone exposure might contribute to gender-typed toy preferences, we cannot organize the influence of socialization processes. Interestingly, external socialization as well as self-socialization might be altered in girls who were exposed prenatally to elevated testosterone concentrations (due to congenital adrenal hyperplasia)
• Therefore, androgen exposure might work in concert with socialization processes to increase male-typical interests and reduce female-typical interests.
• Preference for the colour pink emerges later than sex differences in toy preferences - appears to be moreso a product of girls being given lots of pink toys and objects, and therefore associating positive affective experiences with the colour itself.

Question 5

Sex beyond the genitalia: The human brain mosaic

Answer 5

(Joel et al., 2015)

• Widespread analysis of MRI data.
• Found that most brains are unique “mosaics” of
  features, some more common with females than males, some more common with males than females, and some common with both - as opposed to a single “female brain” and “male brain”
• There are some sex/gender differences in the brain, but there isn’t a distinct “male brain” category or “female brain” category.
• The authors argue that this acknowledgement of the huge variability in human brains, regardless of sex, suggest similar such variability in behaviour within sex/gender groups - which may contribute to discussions about the value of segregating the two groups (e.g., same-sex schools)

Question 6

Corticosteroids and the brain

Answer 6

(Joëls, 2018)

• Corticosteroids - e.g., cortisol - have been linked to the stress response (e.g., vigilance, attention, emotion, memory).
• The brain has two types of corticosteroid receptors - which can mediate both rapid non-genomic (GR - glucocorticoid) and slow gene-mediated actions (MR - mineralocorticoid) in response to stress.
• Directly after stress, attention and vigilance are increased, and areas involved in emotional responses and simple behavioural strategies show enhanced activity.
• In the aftermath of a corticoid steroid peak, areas involved in higher cognitive functions also become activated - allowing individuals to link stressful events to the specific context and to store information for future use.
• Both phases of the brain’s response to stress are important to face a continuously changing environment, promoting adaptation at the short as well as long term. If the initial phase is too strong, the later phase may not be able to sufficiently contain it (i.e., unable to put stress into perspective)
• Balance between these two phases of responding may become compromised after repeated stress exposure, particularly in genetically vulnerable individuals and aggravate disease manifestation. This not only applies to psychiatric disorders but also to neurological diseases such as epilepsy.
• Chronic stress can affect memory, mood, cognition.

Question 7

The Microbiome in Psychology and
Cognitive Neuroscience - Review.

Answer 7

(Sarkar et al., 2018)

• Gut microbes are associated with
  important psychophysiological functions, including neurodevelopment and neurotransmission, emotion and stress, learning and memory, social behavior, autism, and aging.
• Via the HPA-Axis, the microbiome may govern psychophysiological responses to stressors. Mice who are germ-free show greater exploratory behaviours, and abnormal fear-learning processes/fear conditioning.
• Technical and conceptual limitations including low statistical power and lack of mechanistic descriptions prevent a nuanced understanding of microbiome-brain–behavior relationships at present

Question 9

Sleep, Memory, and Plasticity

Answer 9

(Walker & Stickgold, 2006)

• Sleep seems to support learning and memory processes - though the way in which it does so remains largely unknown (i.e., we don’t know which brain plasticity mechanisms underlie sleep-dependent memory processing)
• For example, inadequate sleep before a learning task seems to compromise hippocampally dependent modulation of molecules critically involved in memory
  formation.

Question 10

The social brain hypothesis – thirty years on

Answer 10

(Dunbar, 2024)

• Social brain hypothesis has been used to predict a natural grouping size for humans (Dunbar’s number = 150). Although the population for such social networks is always ~150, there is considerable variation between individuals due to gender, age, personality and social circumstances.
• There is a robust statistical relationship between the
  typical size of a species’ social group and the size of its neocortex.
• Several neuroimaging and comparative studies have shown that mentalising, self-control and other
  advanced cognitive capacities supported by these brain
  regions act as the intermediate bridge between brain size and group size.
• Social brain hypothesis (that the larger brains of primates evolved due to the pressures of social complexity and to enable great co-ordination)

Question 11

Critical periods re-examined: Evidence from children treated for dense cataracts.

Answer 11

(Maurer, 2017)

• Early visual input prepares the brain to respond to later input. Without input at these early stages (e.g., if someone has a congenital cataract) - initial functional improvements fail but there are also sleeper effects (deficits that only manifest much later) - which can be seen in long-term studies of individuals with temporary deprivation from cataracts.
• Visual experience early in life is necessary for the later development of both low level and high level vision - though the effects of early deprivation differ depending on bilateral or unilateral deprivation.
• For lower level vision, the deficits are worse in the previously deprived eye if the deprivation had been unilateral rather than bilateral, but for higher level perception, that pattern reverses.

Question 12

Echolocation in humans: an overview

Answer 12

(Thaler & Goodale, 2016)

• Neuroimaging has shown that the processing of
  echoes activates brain regions in blind echolocators that would normally support vision in the sighted brain, and that the patterns of these activations are modulated by the information carried by the echoes. Sheds new light on just how plastic the human brain is!
• Echolocation (emitting bursts of sounds and listening to the echoes that bounce back to detect objects) may
  enable some blind people to do things that are otherwise thought to be impossible
  without vision, potentially providing them with a high degree of independence.