Brain imaging techniques PET Mikrolesions Single cell Lesions 2-Deoxyglucose Multi-unit Patch clamp EEG & MEG TMS fMRI Optical Imaging millisecundum sec.

Brain imaging techniques

PET

Mikrolesions

Single cell

Lesions

2-DeoxyglucoseMulti-unit

Patch clamp

EEG & MEGTMS

fMRI

Optical Imaging

millisecundum sec min hour day year -3 -2 -1 0 1 2 3 4 5 6 7 8

Log time (sec)

Lamina

Neuron

Dendrite

Synapse

4

3

2

1

0

-1

-2

-3

-4

Lo g Re

sol

uti

on

(m m)

Brain

Column

Patch-clamp recordings: a single channel

Patch-clamp recording

techniques

Even parallel dendritic and somatic patches are possible

A typical result:the I-V curve

Electric activity of the brain on different scales

Lengyel Máté: Egysejt modellek II / Modellek az idegrendszer-kutatásban - ELTE TTK, 2003 tavaszi félévhttp://www.rmki.kfki.hu/~lmate/kurz/

7

Discovery of the electricity in animals:

1792

Galvani, De Viribus - Electricitatis in Motu Musculari.

Lengyel Máté: Egysejt modellek II / Modellek az idegrendszer-kutatásban - ELTE TTK, 2003 tavaszi félévhttp://www.rmki.kfki.hu/~lmate/kurz/

8

Discovery of the electroencephalography (EEG)

1924.

Hans Berger

The first EEG recordThe alpha rythmElectric signs of epilepsy

Investigated the telepathy

Elektroencephalography (EEG) and magnetoencephalography (MEG)

ECIC

V

dVext

IC

IR

RECR

ICIaxial

Iaxial

IC

IR

IC

IR

I ~CSD

I ~CSD

I ~CSD

The source of the EC potential is the sumof the capacitive and resistive currents

The sum of IR is not zero,

But the sum of ICSD

is zero

for the whole cell!

Multi ElectrodeArray

Original current sourcedensity distribution

Sink

Source

Zero

T(d)

The forward problem

Multi ElectrodeArray

Original current sourcedensity distribution

Sink

Source

Zero

T(d)

The forward problem

The origin of the EEG and MEG

Normal resting EEG

F z

C z

P z

A 1

A 2

F p 2

F 4

C 4

P 4

O 2

F 8

T4

T6

F p 1

F 3

C 3

P 3

O 1

F 7

T3

T5

F z

C z

P z

A 1

A 2

F p 2

F 4

C 4

P 4

O 2

F 8

T4

T6

F p 1

F 3

C 3

P 3

O 1

F 7

T3

T5

B and:

D el ta

T heta

A lpha

B eta

G am m a

F z

C z

P z

A 1

A 2

F p 2

F 4

C 4

P 4

O 2

F 8

T4

T6

F p 1

F 3

C 3

P 3

O 1

F 7

T3

T5

EEG imaging with dipole localization

Evoked potentials

20 µV

2 µV

The auditory evoked potential:

Extracellular recordings

Extracellular recordings

Identification of excitatory and inhibitoryconnections by correlation requiresparallel recording of hundreds of neurons.

Active feedback via electrodes

Positron emission tomography (PET)

PET-based functional brain imaging

The MRI machine

The MRI machine

The BOLD response: the basis of the fMRI

High resolution functional brain imagingwith fMRI

Mind-reading with fMRI

Results:Learning on 1750 picturesSelection from 120 new pics: 92%Selection from 1000 new pics: 82%

Direction selective neurons in the motor cortex

Both the motor and the somato-sensory cortex represents the whole body

Each cell is tuned to a specific direction

Brain-machine interface in monkeys

The direction and speed of the planed movement could be determined from the activity of the cells and their directional tuning.

BMI with invasive electrodes

BMI with non-invasiv electrodes

Arm prosthesis driven by the nerves

It is more easy to decode the planed motion from the activity of the peripheral nerves.