Global Brain Activity

What are Brain Rhythms?

1) Rhythmic environment: temperature, day and night, tides…

2) Brain rhythms: sleeping and waking, breathing cycles, steps of walking, stages of night sleep

What is the EEG?

How are Small Fields generated by Pyramidal Cells?

What are the Basic Requirements for Signal Detection?

Basic requirements for signal detection:

1) A whole population of neurons must be active in synchrony to generate a large enough electrical field at the level of the scalp.

2) This population of neurons must be aligned in a parallel orientation so that they summate rather than cancel out.

What is Synchronous Activity?

EEG/Brain Rhythms Correlate with Pathology and Behavioural States

Four basic EEG Phenomena:

How are Synchronous Rhythms GENERATED?

Generation of Synchronous Rhythms - A One Neuron Oscillator

What are the FUNCTIONS of Brain Rhythms?

What are the Behavioural Criterias that classify Sleep?

Behavioural criteria:

1) Reduced motor activity

2) Decreased response to stimulation

3) Stereotypic postures

4) Relatively easy reversibility

How are Dolphins adapted to Predators?

What are the THREE FUNCTIONAL STATES of Sleep

Summary Scheme of Sleep-Wake States

Functions of Sleep and Dreaming

1) Conservation of metabolic energy

2) Cognition

3) Thermoregulation

4) Neural maturation and mental health

Question 1

Imaging Techniques - STRUCTURAL IMAGING

Structural Imaging: Measures of the spatial configuration of types of tissue in the brain (static maps)

1.Computerised tomography, CT

2.Magnetic resonance imaging, MRI

Imaging Techniques - FUNCTIONAL IMAGING

Functional Imaging: Measures the moment-to-moment variable characteristics of the brain that may be associated with changes in cognitive processing (dynamic maps)

1.Positron emission tomography, PET

2.Functional magnetic resonance imaging, fMRI

Structural Imaging - CT Scans

1) Based on the amount of X-ray absorption in different types of tissue.

2) Bone absorbs the most (the skull appears white), cerebrospinal fluid absorbs the least (the ventricles appear black) and the brain matter is intermediate (grey).

3) Used in clinical settings, e.g. to diagnose tumours or identify haemorrhaging or other gross brain anomalies. 

Structural Imaging - MRI

1) 2003 Nobel prize to Sir Peter Mansfield and Paul Lauterbur.

2) Completely safe, so people can be scanned many times.

3) Provides a much better spatial resolution.

4) Provides better discrimination between white and grey matter.

5) Can be adapted for detecting the changes in blood oxygenation associated with neural activity (fMRI).

Sequence of Events in the Acquisition of an MRI Scan

What is the Basic Physiology undepinning Functional Imaging?

Example of PET Scan

Example of fMRI

Functional Imaging - PET Scans

1) Based on blood volume

2) Involves radioactivity (signal depends on radioactive tracer)

3) Participants scanned once or few times

4) Temporal resolution: 30”

5) Effective spatial resolution: 10mm

6) Sensitive to the whole brain

7) Can use pharmacological tracers

Functional Imaging - fMRI

How does fMRI work?

Imaging Techniques - SUMMARY