Memory can be broadly categorized as: sensory memory, short-term memory, long-term memory. Working memory is a concept derived from and related to short-term memory. The different types of memory constitute the sequence of three stages or steps of the memorization process – from sensory to short-term and working memory to long-term memory.

Sensory Memory (Ultra Short-Term Memory) (< 1 sec)

Sensory memory is a very brief  recall of a sensory experience at the end of the original sensory stimuli, and is often considered as part of the process of perception that does not require conscious attention. In other words, sensory memory is an automatic response outside the brain’s cognitive control. For the sensory perceived information to be extracted by short-term memory and processed by working memory, conscious attention is necessary. The brain is created to only process and store those of information that gets attention and are useful at a later time and the rest being ignored and not stored in short-term memory and processed by working memory. Each of the main physiological senses should have a corresponding memory storage:

• iconic memory (visual sense)
• echoic memory (hearing)
• haptic memory (touch)
• smell
• taste

Short-term (working) memory  (< 1 min)

Short-term memory holds a small amount of information (typically around 7 items +/- 2) in mind in an active, available state and is a necessary step toward the next stage of information retention – long-term memory. Is there a distinction between the terminology of short-term memory and working memory? The two concepts although distinctive, but overlaps. Short-term memory emphasizes the ability to store information without rehearsal (repeating) while working memory emphasize the brain’s ability to actively process, manipulates, and controls the information. It is the gateway memory function to consolidate short-term memory into long-term memory where memories can last a lifetime. The time span defined for working memory can be longer (range from less than 1 min to a few days) and is sometimes referred to as intermediate memory.

Long-Term memory (range from a few days to decades and life-time)

Long-term memory is an important component of cognitive function of the brain. Associations of perceived information items are stored. Two major divisions of long-term memory are: explicit memory (declarative memory) and implicit memory (procedural memory):

Explicit memory or declarative memory are those stored information about facts and events that can be retrieved under conscious control. Explicit memory can be further divided into:

• episodic memory: are autobiographical memories that record facts of experiences and episodes of events.
• semantic memory: are memories about knowledge, concepts learned in the past such as the meaning of the words.

Based on the temporal direction of the memories, sometimes declarative memory can be classified alternatively as:

• retrospective memory
• prospective memory

Implicit (non-declarative) memory refer to the ability to perform a task or skilled task using previously stored information of prior experience or knowledge without conscious awareness. Procedural memory and priming belong to implicit memory:

• procedural memory: is the type of memory responsible for the performance of particular actions or tasks. it is automatically retrieved without the need for conscious control. Procedural memory are accessed and used for the carryout of the procedures and tasks that require both cognitive skill and motor skill.
• priming memory: refer to the effect of prior experience on the (increased) responsiveness to future exposure to same or similar stimuli. Priming memory is believed to be retrieved outside of conscious awareness.

The brain’s memory function ages and deteriorates with the normal aging process. Many factors contribute to the age-related memory loss. (see post “Intrinsic and Extrinsic Causes of Age-Related Memory Loss”). Understanding the distinctions among types of memory and how they together forming the sequential stages of memorization process as well as how brain retrieves and uses the stored information for cognitive and motor tasks will help to combat and prevent aging memory loss and diseases. Different memory strategies are developed for strengthen the short-term vs. the long-term memory function. Short-term memory strategies adopt focus, concentration, awareness, attention training. Long-term memory strategies include those such as repetition, paying attention, association, attaching meaning and visualization.