MEMORY

Memory is a relatively permanent storage form of learned information. Memory encoding defines the neural processes that change an experience into memory of that experience. Memory can be viewed in two broad categories called declarative and procedural memory.

• Declarative Memory (Explicit memory) :- It is the retention and recall of conscious experiences that can be put into words. The hippocampus, amygdala and other parts of limbic system are required for the formation of declarative memories. e.g., general knowledge of the world, like names and facts.
• Procedural Memory (Implicit or reflexive memory) :- It is the memory of how to do things. This is the memory for skilled behavior independent of conscious understandings. e.g., riding a bicycle. individuals can suffer severe deficits in declarative memory but have intact procedural memory. Primary areas of brain involved in procedural memory are regions of sensorimotor cortex, basal nuclei and cerebellum.

Memory can also be classified in terms of duration also:-

• Working memory (short term memory):- Registers and retains incoming information for a short time- a matter of seconds to minutes - after its input. e.g., child recalling steps of a recipe while cooking his favorite meal.
• Long term memory:- Short term memories may be converted into long term memories which may be shorted for days to years and recalled at a later time. The process by which short time memories become long term memories is called consolidation.

Working memory is interrupted when a person becomes unconscious from a blow on head, and memories are abolished for all that happened for a variable period of time before the below, a condition called retrograde amnesia.

Anterograde amnesia results from damage to limbic system and associated structures. Patients with this condition lose their ability to consolidate short term declarative memories into long term memories. 

Working memory is susceptible to external interference such as an attempt to learn conflicting information. While, long term memory can survive deep anesthesia, trauma, all of which disrupt normal patterns of neural conduction in brain. Thus, working memory requires electrical activity in neurons.

One model for storage of memory is Long term potentiation.(LTP), in which certain synapses undergo a long lasting increase in their effectiveness when they are heavily used. An analogous process, Long term Depression (LTD), decreases the effectiveness of synaptic contacts between neurons.