Optogenetics refers to using light to control cell activation (e.g: neurons) in living tissue. The cognitive approach to psychology uses two key concepts: information processing depends on internal representations (1) and these mental representations undergo transformations (2). People derive multiple representations from stimuli. Physical representations are activated first, phonetic representations next and category representations last.

The

Each sense collects, filers and amplifies information. Each system has specialized receptor cells that transduce the environmental stimulus into neural signals. The sensory nerves of the body travel up the spinal cord and enter the brain through the medulla and then go to the thalamus. After going through the thalamus, they travel to the primary sensory cortex and

The thalamus is the switchboard of the brain. The reticular formation regulates excitability and forms a sheet around the thalamus and can gate all information (high arousal) or block all information (coma). Arousal is a prerequisite for attention. Selective attention is a covert, cognitive brain mechanism which enables us to process relevant information, thoughts and actions and ignore

Learning refers to whenever experience or interaction with the environment results in changes in behaviour. Memory refers to the complete collection of experiences that have been stored in the brain. Learning occurs in three steps: encoding (1), consolidation (2), retrieval (3).

Iconic memory is the memory storage for visual information. It can store information for

Language production and language comprehension require a mental lexicon, a mental store of information that includes semantic information, syntactic information and details of word form. The mental lexicon is organised by morphemes (1), frequency of use (2), lexical neighbours (3) and semantic relationships between words (4). Lexical selection refers to integrating words into the full sentence.

Sleepwalking involves typically automated behaviour and occurs most often in young children. It occurs more frequently after sleep deprivation and the prevalence is 1%-5%. It typically occurs during the deepest stages of sleep and the frontal cortex is deactivated during sleepwalking.

In normal sleep, there are successive sleep stages. Cycles last ±90 minutes. Deep sleep