Inside Your Head 2025 Term 2 - Set 3

Synapse

• The tiny gap at the junction between two nerve cells which nerve signals must cross

1. The electrical impulse is travelling along the first axon

2. Neurotransmitters (chemical messengers) are released from the nerve ending of the first neuron

3. The neurotransmitters diffuse across the synapse (the gap) to bind with receptor molecules on the membranes of the second neuron

4. The second neuron is stimulated and transmits the electrical impulse

Explain how a synapse transmits messages across the synaptic cleft [4 marks]

A synapse transmits messages across the synaptic cleft through a process that involves an electrical impulse travelling along the first axon. The neurotransmitters are then released from the nerve ending of the first neuron. The neuro transmitters diffuse across the synapse to bind with receptor molecules on the membranes on the second neuron. The stimulates the second neuron which transmits the electrical impulse

Mirror Neurons and Human Evolution

• Ramachandran (2011) has suggested that mirror neurons are so important that they have effectively shaped human evolution

• The uniquely complex social interactions we have as humans require a brain system that facilitates an understand of intention, emotion and perspective

• Without these cognitive abilities we could not live in the large groups with the complex social roles and rules that characterise human culture

• Ramachandran suggests that mirror neurons are absolutely key to understanding the way humans have developed as a social species

Mirror Neurons

• Mirror neurons dates back to the 1990s in the town of Parma Italy, an unanticipated scientific breakthrough was made in the lab of a neurophysiologist, Giacomo Rizzolatti

• It was here that researchers first observed the peculiar phenomenon of mirror neurons in action within the brain of Macaque monkeys

• During their experiment they noted that the monkey neurons fired not just when they performed an action such as grabbing a piece of fruit, but also when they witnessed another monkey perform the same action

• It was as if the monkeys were living vicariously through each other's experiences

• This accidental discovery was the first piece of a puzzle that promised to unlock the mysteries of empathy and social interaction

• This ground breaking discovery provided the first hint of our brain's ability to mirror the action of others

• These cells in our brain fire not only when we perform an action, but also when we observe someone else performing the same action

• It's as though our brain is mirroring the behaviour of others, hence the name mirror neurons

• Research has shown that mirror neurons play a crucial role in understanding the actions of others

• They act like a neural Wi-Fi connection us to the minds and emotions of those around us, enabling us to feel what they feel

• This is the biological bases of empathy, a fundamental human trait that allows us to share and understand each other's feelings

• Mirror neurons are the engine behind learning through imitation

• E.g. Babies learning how to smile; learning a dance move by watching someone

• Some scientists propose that conditions like autism characterised by difficulties in social interaction and communication could be linked to a dysfunction in mirror neuron

Broken Mirror Theory (Mirror Neurons and Autism Spectrum Disorder)

• Ramachandran and Oberman (2006) have proposed the ‘broken mirror’ theory of ASD

• This is the idea that neurological deficits including dysfunction in the mirror neuron system prevent a developing child imitating and understanding social behaviour in others

• This manifests itself in infancy when children later diagnosed with ASD typically mimic adult behaviour less than others. Later, problems with the mirror neuron system lead to difficulties is social communication as children fail to develop the usual abilities to read intention and emotion in others

Neurotransmitter

Is a chemical messenger that carries signals between neurons, or from neurons to muscles

Agonist

Promotes transmission of ACh

Antagonist

Blocks transmission of ACh

Acetylcholine (ACh)

• Location: central nervous system and the parasympathetic nervous system

• Function:

  • Muscle movement (contraction)

  • Smooth muscle like the heart

  • Memory and learning

  • Motor neurons

• Too much acetylcholine is linked with increased salivation, muscle weakening, blurred vision, and paralysis

• To little acetylcholine is linked to learning and memory impairments, as well as being shown to have links to dementia and Alzheimer's, according to research

Acetylcholine (ACh) on memory

• ACh is a neurotransmitter which has been linked to synaptic plasticity in the hippocampus and it seems to play an important role in learning and short-term memory via the cholinergic system

• The cholinergic system is a system of nerve cells that uses acetylcholine in transmitting nerve signals. Memory processing and higher cognitive functioning are dependent on the cholinergic system

Martinez and Kesner ACh in memory formation

• 1991

• Aim: to investigate the role of ACh in memory formation

• Procedure: experimental study using rats. They were trained to run a maze. They were divided into three groups:

  • Group 1: received injection with scopolamine (blocks ACh receptor sites, reducing available ACh) - antagonist inhibiting

  • Group 2: received injection with physostigmirie (blocks production of cholinesterase (enzyme) which cleans up ACh from the synapses) leading to more available ACh - agonist promotes neurotransmission

  • Group 3: the control group - injected with placebo

• Results:

  • Group 1 had problems finding their way through the maze and made more mistakes

  • Group 2 ran quickly through the maze and made few mistakes. Group 2 was quicker than the control group

• Evaluation:

  • The study shows that ACh is important in memory since the rats showed different memory capacity depending on ACh level. Since this was a controlled laboratory experiment, it can be concluded that the level of ACh is one factor that affects memory but the neurobiology of memory is very complex

Sperling et al. Study

• 2002

• Aim: to investigate how people with early Alzheimer's disease use their brains during memory tasks, especially focusing on areas activated during memory encoding (storing new information)

• Method:

  • Participants included 10 patients with early Alzheimer's disease and 11 healthy older adults

  • They were shown pictures of scenes while their brains were scanned using fMRI (functional magnetic resonance imaging)

  • Later, participants were asked to recognise which scenes they had seen before

  • Researchers compared brain activity during the learning (encoding) phase

• Results:

  • The healthy adults showed strong activation in the hippocampus and other memory-related brain regions while viewing the pictures

  • The Alzheimer’s group showed less activation in these areas during encoding

  • Their memory performance (how many scenes they remembered) was also worse than the healthy group

• Conclusion: the study suggests that people with early Alzheimer’s have impaired memory encoding, which may be linked to reduced activation in the hippocampus and lower levels of acetylcholine. This helps explain why they have difficulty forming new memories, and supports the use of ACh-boosting treatments to slow memory loss

How do acetylcholinesterase inhibitors (agonists) work?

• prevent enzyme called acetylcholinesterase from breaking down acetylcholine in the brain

• as a result, an increase concentration of acetylcholine leads to increased communication between nerve cells (improves memory)

How does ACh affect memory?

• more ACh = better memory

• less ACh = worse memory

• ability to encode memories

• encoding and retrieving memories