brain waves

Question 1

Define brain waves

Answer 1

Summated electrical activity in a small patch of tissue.

Question 2

3 factors that influence brain waves

Answer 2

Behavioral state
Location of recording electrode
Geometry of neurons ie are all axons aligned?

Question 3

Brain waves characteristic patterns

Answer 3

Delta 0.1-3 Hz Deep sleep (SWS)
Theta 3-8 Hz Movement, planning, homeostatic behaviors, navigation
Alpha-8-12.5 Hz Quiet focus, movement initiation
Beta-12.5-30 Hz-Waking, active concentration
Gamma-30-100+ Hz -Memory, navigation, imagination

Question 4

What are some characteristics of theta oscillations ie where do they originate from?

Answer 4

inhibition: interneurons that originate from the basal forebrain (medial septum) which project to hippocampal pyramidal neurons that receive excitatory input from the entorhinal cortex
Have HCN channel
Long range projections
Accompany movement - visual flow, repetetive stereotype movements, speed variance

Question 5

Which type of oscillations are dominant during movement, eating, grooming and sex?

Answer 5

Theta

Question 6

Characteristics of gamma oscillations

Answer 6

30 (slow gamma)-100+ Hz( fast gamma), very fast oscillations
Local projections
Generated by 1) Interneuron-interneuron model
2) Pyramidal-interneuron model
Connected with memory and higher function
Nested within theta oscillation during navigation

Question 7

Characteristics of place cells

Answer 7

CA1 pyramidal cells or CA3 parasubiculum cells
Respond to single location in environment by increasing firing rate
Allocentric/external cues
Change between environments (remapping) but stable over time

Question 8

Characteristics of grid cells

Answer 8

Layer II of medial Entorhinal cortex
Pyramidal/Stellate cell or both
Cells change firing rate in tessellated field
Stable over time but only slightly shift instead of remapping

Question 9

Difference between grid and place cells in terms of stability over time

Answer 9

Place cells and grid cells are both stable over time. However, place cells change between environments (remapping) but grid cells only slightly shift instead of remapping

Question 10

Method to test for navigation scientifically

Answer 10

Firing rate heat map

Spatial autocorrelation

Question 11

True/False Navigation is only limited to grid and place cells

Answer 11

False. Other types of cells exist eg head direction cells, border cells, speed cells, conjunctive cells

Question 12

Reduction of theta oscillations disrupts the spatial computations of grid cells. True/false

Answer 12

True

Question 13

Define place cell sequence

Answer 13

The concentrated firing of place cells nested within theta cycle oscillations in a predictable order.

Question 14

Name a possible model of how items are associated in memory

Answer 14

Place cell sequence

Question 15

Define theta phase precission

Answer 15

Firing of cells at progressively earlier phases of a theta cycle as an animal traverses a place field

• cells prefer descending wave of theta
• negative correlation between spiking phase and an animal’s location in a place field

Question 16

Models to explain theta phase precission

Answer 16

1. Dual oscillation model : 2 oscillations that are not in phase
2. Asymmetric ramp model: Pyr cells rhythmic inhibition+ asymmetric excitation. Excitation overpowers inhibition
3. Network models: Oscillations from EC and CA3 arrive at slightly different times in the theta cycle, controlling PC excitation

Question 17

Describe the network model that explains theta phase precission

Answer 17

Intra MEC/HC plasticity
Combination of inputs ie MEC, CA3, septum
Oscillations from EC and CA3 arrive at slightly different times in the theta cycle, controlling pyramidal cell excitation

Question 18

How does theta cell precission double the amount of info in a neural signal?

Answer 18

Rate CODE: Location can be deduced by how much a cell is firing
Temporal code: When a cell is firing relative to the global LFP

Question 19

How does theta phase precission influence synaptic plasticity?

Answer 19

TPP compresses behavioral sequences eg navigation trajectories into time scale for synaptic plasticity

Question 20

Name 3 substrates of the global neural code

Answer 20

Rate coding, temporal coding and simple neurophysiological mechanism

Question 21

Is the phase precession of EC cells dependent on hippocampal activity?

Answer 21

No. Phase precession of EC cells is independent of hippocampal activity . CA1 place cells may inerit the property of phase precession

Question 22

Do place cells exhibit theta phase precession?

Answer 22

CA1 place cells may inherit the property of phase precession, packaging environmental info into a possible neural code