Sensory memory is the shortest-term element of memory. It is the ability to retain impressions of sensory information after the original stimuli have ended. It acts as a kind of buffer for stimuli received through the five senses of sight, hearing, smell, taste and touch, which are retained accurately, but very briefly. For example, the ability to look at something and remember what it looked like with just a second of observation is an example of sensory memory.
The sensory memory for visual stimuli is sometimes known as the iconic memory, the memory for aural stimuli is known as the echoic memory, and that for touch as the haptic memory.
In a study on Alzheimer’s researchers showed that diminished iconic memory may be an early indicator of an increased risk for Alzheimer’s disease.
“People with mild cognitive impairment have very short visual memory,” explained lead researcher Zhong-Lin Lu, a professor of psychology at the University of Southern California. “Visual memory is the first part of the memory system, and for people with mild cognitive impairment, their short-term visual memory almost does not exist.”
In their study, Lu and his team tested iconic memory in 16 people, aged 65 to 99. All had mild cognitive impairment. During the test, the people were briefly shown a computer screen that had letters placed in various places on the screen. After looking at the screen for a moment, the people were asked to tell the researchers the position of each letter.
The researchers found that compared with younger or older people without cognitive impairment, the iconic memory in those with mild impairment faded faster. “Many of these subjects will get Alzheimer’s disease in the next 10 years,” Lu said.
The researchers believe that, with further study, a screening test using iconic memory could be developed that would help determine a person’s risk for Alzheimer’s. “This measure could help us predict whether people will have Alzheimer’s disease or not,” Lu said.