Introduction
Evidence suggests that brain memories are not whole; rather, pieces of information stored in different areas of the brain are combined to create memories (Matlin, 2012). This explains why recalled information is not entirely accurate. Encoding, storage and recall of skills and facts (semantic memory) or experiences (episodic memory) involve different parts of the brain. This implies that there is a close relationship between memory processes and brain functioning.
Working and Long-term Memories
Over the years, there has been an intense debate on whether working and long-term memories are related. While there are many similarities between the long-term memory (LTM) and working memory (WM), distinct differences also exist between the two. One difference is that the functioning of LTM does not require the activation of WM.
A study by Morgan et al. (2008) revealed that many qualities of LTM such as procedural memory and motor skills do not depend on the working memory. However, episodic memories, which rely on past experiences, may at some point involve the activation of the working memory (Morgan et al., 2008).
Long-term memory has two distinguishing properties; (1) it has no capacity limits and (2) it lacks temporal decay associated with short-term memory (Morgan et al., 2008). In contrast, WM encompasses tasks of short-term memory that demand more attention, but are not directly associated with cognitive aptitudes. It is a combination of different memories working together, including some components of the long-term memory, to organize information in the working memory into fewer units in order to reduce the working memory load.
Both WM and LTM are affected by the level of semantic processing or encoding in the brain. LTM is known to be affected by the qualitative depth of initial memory encoding (Matlin, 2012).
For example, it has been established that encoding during semantic processing results in improved long-term memory of episodic items compared to recall of visual or phonological items (Morgan et al. 2008). Similarly, since the performance of WM depends on the level of processing at the encoding stage, semantic processing can lead to improved WM.
Memory Formation in the Brain
Stadthagen-Gonzalez and Davis (2010) propose that memory is formed through dendrite-axonal networks, which become more intense with an increase in the number of events stored in the LTM. Stadthagen-Gonzalez and Davis (2010) also postulate that memory storage involves different cortical areas of the brain, where the sensory experiences are processed.
The neural (brain) cells involved in memory formation undergo physical changes through new interconnections as cognitive and perceptual processes in the brain increase. The synapses (a vast system that connects neurons) are involved in the formation of interconnected memories or neural networks.
It is the neural networks that facilitate the formation of new memories. Karpicke and Roediger (2009) postulate that, through a closely related activity (relayed through similar synapses), a new memory is formed causing changes to the neural circuit to accommodate the new item.
Also, new neurons can be joined to the circuit, if they are correlated with previously formed neural networks (Matlin, 2012). Long-term potential (LTP) is associated with reverberation (depolarization) in the post- and pre-synaptic neurons during learning. It is induced through prolonged stimulation of synapses during learning. New memories are maintained through repetitive excitation of LTP, which increases the release of neurotransmitters that can persist for several days or even months.
Adaptive Recall and Forgetfulness
Evidence suggests that the amygdala and the hippocampus regions of the brain interact during the formation of verbal and visual memory (Matlin, 2012). However, the amygdala identifies and stores emotionally important information while the hippocampus creates new neural networks for cognitive material.
It is through the amygdala-hippocampus interaction that emotionally important memories are recalled. The same applies for less emotionally significant events, which are less arousing. Thus, personal and emotional experiences are easily recalled than neutral events. It also explains why reinforcements improve memory while damage to hippocampus and amygdala results to impaired memory functioning.
From an evolutionary standpoint, the neural relationship between the hippocampus and the amygdala is an adaptive response to life experiences. Karpicke and Roediger (2009) suggest that stressful conditions affect the processing and storage of new memories. Also, the retrieval strategies of the hippocampus may be repressed under stressful conditions.
Consequently, it becomes adaptive to remember relevant and emotional memories for survival purposes. Also, through amygdala-hippocampus interaction, it becomes adaptive to forget or repress some traumatic or unpleasant memories in order to maintain normal cognitive functioning.
Accuracy of the Memories
Studies have shown that human recollections are often not accurate. This raises questions regarding the extent of accuracy of the memory. Unsworth and Engle (2011) demonstrate that the hippocampus-amygdala interaction is essential in memory encoding and retrieval, with the amygdala regulating information encoding, storage and recall from the hippocampus.
Thus, for some time, the recall accuracy of emotionally arousing events is high compared to neutral ones. Evidence also suggests that physiological changes in the level of arousal affect the way memories are replayed. For instance, Unsworth and Engle (2011) show that, at the encoding stage, the level of activation of amygdala influence memory retention while its damage impairs memory arousal. This highlights the fact that emotional arousal enhances memory accuracy, at least in the short-term.
Memory Aids for Memory Impaired Individuals
Memory impairment or loss may have a number of causes, including neurological diseases, aging, trauma, stroke, or brain injury. Individuals suffering from poor memory, amnesia and PSTD can benefit from memory aids that enhance their memory. Prospective memory (PM) aids can help such people to recall essential actions in their daily lives (Matlin, 2012). They are normally external aids that facilitates semantic memory or systems that allow caregivers to monitor the cognitive functioning of patients with memory problems.
Karpicke and Roediger (2009) group memory support systems into three; assurance systems that monitor a person’s cognitive health at home or care setting; compensation systems, which involve functionalities that accommodate the user’s memory impairments; and assessment systems, which are technologies that continuously monitor the cognitive status of users under rehabilitative care.
Developers of these systems rely on the knowledge regarding the functioning of the brain and memory encoding processes to make memory aids. Also, understanding the type of memory affected can help in the treatment of the individual through psychoanalysis.
The Effect of Age and Environment
Age and environment influence several cognitive and physical abilities in humans. While some types of memories (semantic/conceptual memory) increase with advanced age, others such as episodic memory (specific events) decrease with age (Matlin, 2012). Elderly people often experience difficulties in performing high cognition-demanding tasks because aging impairs memory processes such as working memory, encoding and sensory functioning.
This leads to a decline in memory, reasoning and problem-solving ability. However, automatic processes that do not involve much cognitive resources remain unimpaired during old age. Karpicke and Roediger (2009) suggest that old age does not significantly affect memory processes as attention-demanding tasks may, with time, become automatic.
Environmental conditions also influence the development and maintenance of memory. The environment affects memory through neural mechanisms. Environmental enrichment through memory-based tasks and physical activities increase hippocampus volume by promoting cell (neuron) proliferation (Matlin, 2012). Also, problems associated with social environment such as stress affect memory and brain functioning in humans.
References
Karpicke, J., & Roediger, H. (2009). The Critical Importance of Retrieval for Learning. Science, 15(3), 966-968.
Matlin, M. (2012). Cognition. New York: Wiley
Morgan, C., Hazlett, G., Baranoski, M., Doran, A., Southwick, S., & Loftus, E. (2008).
Accuracy of Eyewitness Identification is significantly associated with performance on a standardized test of face recognition. International Journal of Law and Psychiatry, 30, 213–223.
Stadthagen-Gonzalez, H., & Davis, J. (2010). The Bristol norms for age of acquisition, imageability and familiarity. Behavior Research Methods, 38(3), 598–605.
Unsworth, N., & Engle, R. (2011). Simple and complex memory spans and their relation to fluid abilities: Evidence from list-length effects. Journal of Memory and Language, 54(3), 68–80.