A concept from the Ghost in the Shell universe, a cyberbrain is a set of implants which wire one's brains directly with a computer network.

Would such a thing be possible?

A human brain is made out of hundreds of billions of brain cells and hundreds of trillions of connections between them.

A single cell, a 'neuron', has threads connecting it to other neurons, enabling electrical impulses to travel through. 'Dendrites' are the threads which are usually accepting the impulses, and the long 'axon' usually forwards them.

Depending on the chemical transmitters present, the signal is altered - each connection has a 'weight' by which it modifies the strength of the impulse.

Human intelligence emerges from the grand dance of impulses in the human brain. It also shows a kind of persistency, memories formed by the 'weights' of the connections.

A shell hosting a ghost.

(As of yet, this is only a single level of operation in the human brain. The complexity of the human brain eludes formal science and will do so for a while.)

This level (the neural network level) can be simulated by mathematical formulae and their application in computer technology.

From here on, it doesn't require too much a stretch of imagination to envision an interface between the network of the human brain and artificially created computer networks.

What would be the implications of such an interface?