They are: 1) long-term memory 2) short-term memory and 3) sensory memory Long-term memory Long term memory refers to those memories that are stored in the brain for a considerably prolonged period of time with out any loss. Here when an idea is stored in long-term memory, the information is stored in a semantically encoded format. As a result of this it is easier for us to remember a telephone number by virtue of repeating the same but it is difficult to memorize a random ten digit number.
For the later case the encoding format is acoustic and hence the information is stored in short-term memory. Baddeley, the great researcher on human memory has found out that when given a test to recollect words uttered was given to a group of respondents the result was that people failed to recall words with same meanings like small, tiny, minute etc.. Short-term memory This is a much more volatile memory that stores information just for a period of several seconds to few minutes with out memorizing it by heart. George A. Miller, held various demonstrations and the conclusion was that the storage capacity of short -term memory was just 7 ± 2 entities (he presented a paper entitled "The magical number 7±2"). In the present day the projected capability of short-term memory is still less. But hen the same group of words or letters, for an example is presented in different order, greater are the chances for recollecting it. For example it is difficult to recollect the string FBIUNOASDFUS But when the same string is presented as below, greater chances re there for anyone to recollect it FBI UNO ASDF US.
In the first combination of letters the information was lying stray with no order to memorise, whereas in the second one, they have an opportunity to memorise it as bits which could be identified to something that they know. Short-term memory relies on the phonemes and the acoustic symbols for retaining information. Visual codes are rarely converted to short-term memory. Conrad a renowned researcher on human memory found out that the subjects of his experiments had difficulty in identifying and recollecting acoustically confusing phonemes and words like he, ghee, bee, see, etc..
Sensory memory This kind of memory refers to the memory that is retained in the receivers mind for about 200 to 500 milliseconds, once the information is acquired. Hence this is highly volatile and short-life memory. Sensory Memory can be identified as the ability to identify the specific features of an item, let it be a sound or an object by virtue of an observation of the same for a fraction of a second. George Sperling is the pioneer to conduct experiments on Sensory Memory. Respondents were provided with a set of 12 letters, which were made into 3 rows of four each.
After completing a small introduction, the candidates were then made to hear either a high, medium or low pitch tone, providing them info regarding which of the rows to report. On the base of this experiments, Sperling demonstrated that the range of sensory memory was about 12 items, but also found that it degenerated at a much more faster pace (it only had the life p of a few milliseconds and hence highly momentary). The main negative part of this kind of memory is that any sort of rehearsals do no not enhance the longevity.
What is memory? Present day neuroscience and scientists are with the stream of thought that memory is a group of neural connections which are encoded so as to retrieve for future references. This sort of memory encoding may happen in different parts of the brain. Thus, a network of neural communication is likely to link various parts of the brain. The strength of the memory depends up on the strength of the neural connections. Recollection or calling back of any bit of memory can happen whenever a positive stimulus that trigger the particular part of the networked neural connections.
As a result of this, when a part of the brain gets damaged, the neural network present there and obviously the memories associated with the particular neural connections is lost for ever. Why do we forget things? Forgetting can better be explained as an inability to keep memories secure. This is a condition when ideas and images perceived are either lost in full or part. The reasons for forgetting are many. The prominent factors that lead to forgetting include. 1. Poor encoding (this is why we forget dreams that we see while asleep. Encoding refers to converting the sounds, visuals, taste, smell tc.
To corresponding chemical / neurological codes); 2. Unavailability of a retrieval mechanism (if there is no proper stimuli to trigger the memory, the information remains dormant); 3. Time factor : when a recent incident happens, the older data are sometimes wiped off from memory (We tend to forget exact dates of our vehicle insurance, when you have some 5 cars and 4 cruisers! ); 4. Continuous similar experiences (You may have memories of the first instance when you visited London, but if you fly London Every year, you many not remember when you landed for the fifth time! )
The Chemistry of memory! The human brain is a highly complicated organ with more than 20 billion nerve cells (neurons), about 150 trillion nerve connecters or synapses; an average of 7500 synapses per neuron within the brain, anyway, some neurons may have as many as 900,000 as well. Due to repair and safety from glial cells that protects the neurons, some nerve cells will be alive till the organism cease to live, however, it is calculated that about 85,000 neurons wear out everyday in the brain. The most prominent doubt regarding memory is the place / location where it is being stored.
It was in 1960’s that the theory of Long-Term Potentiation (L. T. P) and it counter theory called opposite Long Term Depression came in to existence as molecularmemory postulates. Long-term potentiation refers to the reinforcement of neuron relations through elevating synaptic ion movements. In all connections of neurons there exists a synapse through which chemical neurotransmitters moves unhindered from the axonates and axons of the transmitting cell to the dendrites of the corresponding receiver cell.
Neuro-transmitters like acetylcholine, gamma-aminobutyric acid, glutamate, serotonin, norepinephrine function in free flow of complex electrical signals between nerve cells, muscle cells and sensory cells. Where as in the mean time, inside the cell, the protein pumps located in the cell membrane and channels frequently retains a constantresting potential of - 70 m V by virtue of moving sodium cations on the outer part of the cell against a specific gradient.
Presence of neurotransmitter into a receiver neuron located in the membrane part of a post-synaptic dendrite triggers and starts de-polarization of the specific membrane by the influence of calcium and sodium ions, this again results in the building of voltage-gated sodium and calcium channels to unlock, permitting rapid flow of calcium and sodium ions, this is then followed by the inflow of potassium ions . as a result of this ion flow, depolarization happens once again to + 40 m V.
As a result of this continuous process, “action potential” rapidly happens in the cell membrane to the axon , axonates and the pre-synaptic cleft, thus repeating this each and every time the signal reaches a neuron. Once the action potential has completed, the voltage gated channels close by themselves, and the potassium and sodium pumps makes the cell membrane to return to their original potential. All these happens in milliseconds, thus permitting multiple contradictory signals in swift momentum..
Memory Disorders The branch of Human psychology and neurology is the basis for the diagnosis and treatment of many of the known memory disorders. In general the loss or degeneration of memory is termed as amnesia. Amnesia is of different categories. Analysing it can reveal the various forms of it and helps in the proper treatment as well. Many neuron related conditions like Alzheimer's disease may also result in full or partial memory loss.
Hyperthymesia, also called hyperthymesic syndrome, is a serious memory disorder which has adverse effect on retention of personal memory. Some sort of memory loss can be symptom of hypothyroidism a severe medical condition. Increasing oxygen supply to the brain, is considered as one among the foremost techniques to improve memory. This can be achieved by doing exercises like swimming, bicycle riding, gymnastics etc.. Tips to improve memory
Many factors to improve memory was furnished by the report published by ‘The International Longevity Center’ in the year 2001 (pages 14-16) The study recommends to stick to the following to improve memory stay intellectually active through learning, training or reading, keep physically active so as to make blood circulation in the brain more active, socialize, reduce stress to the maximum possible extend, observe regular sleep timings, avoid depression or emotional strain and good nutrition.