L1 - 2

Question 1

The isotropic fractionator (method)

Answer 1

1) Isolate all nuclei (grind up brain)
2) Stain DNA with Fluorescent dye
3) Count sample using Flow cytometry – sample x brain volume = total cells
4) Stain subsample for Neuronal nuclear marker, count to get proportions of neurons

Question 2

T/F: There are equal numbers of neurons and non-neuronal cells

Answer 2

T – 86 billion neurons, 85 billion non-neuronal cells

Question 3

Are there more neurons in the cortex, rest of the brain or in the cerebellum?

Answer 3

Most in cerebellum, then cortex, then rest of brain

Question 4

Cortical neurons estimated to each have around x synaptic inputs

Answer 4

7000

• A trillion synapses per cubic cm
• 1.5 x 10^14 total synapses in cortex

Question 5

As we have so much data in the brain, compressing and chunking is inevitable but?

Answer 5

It leaves gaps

Question 6

What is the top down issue?

Answer 6

We learn to see what we see - can only see things we’ve learnt to see e.g. kittens raised in environment with only vertical features, they can never see horizontal lines after that critical plastic period

Question 7

Is vision veridical (truthful)?

Answer 7

No -it is not a perfect representation of the world; it is a construction of the world based on how our systems work

Question 8

Is there data compression in visual pathway?

Answer 8

Yes
-10^10 bits sec = retina
-10^8 bits sec = optic nerve (approx. 10^6 ganglion cell axons per eye)
-10^4 bits sec = layer IV of V1 (Primary visual cortex)
And after V1 – at some point, info is added that is not from the retina

Question 9

Müller-Lyer illusion

Answer 9

Optical illusion consisting of a stylized arrow. When viewers are asked to place a mark on the figure at the midpoint, they invariably place it more towards the “tail” end.

When we see an object, it’s always in the context of how we think the world is organised

Question 10

Inverse problem

Answer 10

Using observed data to reconstruct model (causation) e.g. Measuring electrical activity in scalp then figuring out what generated it

The same pattern of retinal activation can be produced by different configurations of objects in the visual field. All the red lines in the world make the same retinal image – how can we determine which interpretation is correct?

Question 11

Genes are abstract – no single developmental result but a type of developmental pathway or predisposition

Answer 11

Genes are abstract – no single developmental result but a type of developmental pathway or predisposition

Question 12

Engrailed gene

• It was discovered in drosophila where it is crucial for patterning processes – segmentation of epidermis
• There is a homologous gene in mammals. Null mutation dramatically affects cerebellar and limbs
• Fly engrailed gene can act as replacement for mouse without mouse engrailed gene

Answer 12

Engrailed gene

• It was discovered in drosophila where it is crucial for patterning processes – segmentation of epidermis
• There is a homologous gene in mammals. Null mutation dramatically affects cerebellar and limbs
• Fly engrailed gene can act as replacement for mouse without mouse engrailed gene

Question 13

Pax 6/eyeless can cause ectopic eye development when misexpressed in a different body region (e.g. elbow) – but this works if the gene is taken from animals with completely different types of eye
-it has a type of developmental pathway: eye-ness and in mammals it also has some limb-ness

Answer 13

Pax 6/eyeless can cause ectopic eye development when misexpressed in a different body region (e.g. elbow) – but this works if the gene is taken from animals with completely different types of eye
-it has a type of developmental pathway: eye-ness and in mammals it also has some limb-ness