**2. Human computer interactions**

In general, HCIs are related to the adaptation of a human and a computer. HMIs adapt human demands to the machine. Human computer interface operation requires the effective interaction of two sides; user and system. Here, a system can be an integrated system of computers and a word speller, a robot arm, a powered wheelchair, house appliances such as door locks, TVs or musical instruments, etc. In order to reflect intent/demands, instead of overt speaking or muscular movements, other bio-signals can be used. Effective BCIs may serve as assessment tools and adaptive systems for HCI for able-bodied people and be proven for people with severe motor neuron diseases.

Research in this field is typically focused on several areas of improvement for HCIs in order to increase its usefulness and effectiveness. These areas are:

	- a. Accuracy
	- b. Reliability
	- c. Fast
	- d. Robustness

In short, HCI should reflect user demands and expectations accurately and quickly. The next sections of this chapter will introduce the EEG, EOG, NIRS based systems, as they are technologies that show much promise. In addition to these technologies, electrocorticography (ECoG), functional magnetic resonance imaging (fMRI), galvanic skin response (GSR) and heart rate (HR) based systems; and multi-modal integrated design rationale are introduced briefly.
