1. SISSA limbo CÉREBRO, VIDA e CULTURA We can easily describe the brain;
but can we understand,
focusing on one of its parts,
one of its multiple functions,
how does it work?
SISSA
limbo
CÉREBRO, VIDA e CULTURA
18 de Dezembro de 2008
Alessandro Treves

2. THE HIPPOCAMPUS
a structure which remains stable and self-similar across mammalian species H
opossum
human DG H
monkey

3. reptiles ≠ mammals ≠ birds
but… has it always been like that?
human
cat
rat
platypus
lizard DG
reptiles ≠ mammals ≠ birds
CA1
CA3
The medial pallium
has been with us for over 300 million years…
 hippocampus
or over 200 million years…

4. Is the hippocampus what we use to navigate?
…or is it used to recollect from the past
salient episodes of our lives?

5. A B C ’global remapping’
Consider what happens in the hippocampus when changing context A B C
’global remapping’
CA3 charts can be described as a (discrete?) number of continuous attractors, with minimal overlap among them

6. Discrete attractors, with units arranged in a cortical network+
position
context
..use multiple charts
to code environments...
CA1
CA3 DG
Visual
Olfactory
Auditory
Vestibular
Touch
Taste EC
Object 2 in position 1
Object 1 in position 2
Object 1 in position 1
..use the sheet
to code position...
Discrete attractors, with units
arranged in a cortical network

7. recurrent collaterals
Neural Computation
The full model
perforant path
The starters’ model DG
mossy fibers
CA3
recurrent collaterals
noise σ2

8. CA3 and CA1 show similar activity
although they differ at coding
similar contexts, quantitatively 

11. ? ≠
1 chart ≈ 1/a patterns
 fewer sparser charts

12. a fraction of a bit
synapse
(as for any associative
memory model so far)
Can we reach this limit?
Karel’s movie