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RESOLVING AND MANIPULATING

NEURONAL NETWORKS

Pan European Networks: Science & Technology

19

www.paneuropeannetworks.com

208

PROFILE

T

he day-to-day life of mammals relies on sensory

perception, behavioural adaptation to an ever-changing

environment, and on cognitive processing. These key

abilities depend on neuronal networks of different complexity. Over

the last decades an impressive effort has been made to

understand the relationship between the neuronal and the

behavioural/cognitive level.

Despite enormous amounts of detailed information about

neurons and their assembling into small and large scale networks,

a mechanistic explanation of how such groups or even single

neurons account for a particular behaviour is still missing. This is

due to three main drawbacks of past experimental approaches.

First, the majority of studies investigated neuronal networks in

isolation from the rest of the brain and their functional readout.

Placing the knowledge gain of these studies back into a systemic

context is a challenging task, which has been rarely achieved. As

postulated by Donald Hebb more than 60 years ago in his

functional cell assembly hypothesis, ‘the problem of

understanding behaviour is the problem of understanding the

total action of the nervous system and

vice versa’

(Hebb, 1949).

Second, most past studies linking neuronal networks with their

systemic functions were correlative rather than causal. Neuronal

activity has been explored mainly by electrophysiological and

imaging methods while the animal performed a specific task. This

design allows the correlation of spatiotemporal network dynamics

with the respective behavioural state. In this way, fundamental

principles of cognitive function, e.g. formation of neuronal space

representation in the hippocampus and entorhinal cortex or

stimulus detection and sensory processing, have been elucidated.

However, causal interactions between distributed networks and

behaviour have only recently become accessible due to refined

analysis methods and new techniques that allow highly specific

manipulation at the cellular level.

Third, in recent decades the focus of the scientific community has

shifted towards a molecular and biochemical perspective. It is

now time to restore systems neuroscience in order to decode the

function of neuronal networks in the living organism. All these

facts justify the urgent need for strengthening research at the level

of higher, integrated brain functions. The prerequisite for

addressing this challenging issue in neuroscience – how

behavioural abilities map onto neuronal networks – is the

substantial technical progress and gain of knowledge over the last

few years, to which German research groups have contributed

significantly. The impressive development of new recording and

imaging techniques, as well as of neuroengineering, optogenetic

and analytical tools, in recent years had a profound impact on

neuroscience. Thus the time has now come to bind experimental

systems physiology with neurotechnology and analysis/modelling

of network dynamics in an interdisciplinary and seminal

collaborative endeavour.

Interdisciplinary collaboration

The Priority Program 1665 aims to identify causal relationships

linking the activity of single neurons and networks to behaviour.

This undertaking relies on the long and rich tradition of systemic

neuroscience in Germany, pioneered by Otto Creutzfeldt, Bert

Sakmann, Erwin Neher,Wolf Singer and Hans Dieter Lux. The

interdisciplinary consortium initiated in 2013 brought together the

available expertise in Germany. There is an emphasis on

sensory-motor and cognitive processing, and investigations are

performed at different levels of network complexity, ranging from

single neurons and microcircuits to large scale cortico-subcortical

neuronal networks, and both adult and developmental aspects

are covered.

Specifically, the members of the consortium monitor and

manipulate neuronal activity using new experimental tools, which

are developed and validated in collaborative efforts centred on

behavioural/functional readouts. Analysis of network dynamics

The Priority Program 1665 combines neuroengineering and biophysics

with physiology and computational neuroscience to decipher the

mechanisms of brain encoding

THE HUMAN BRAIN