Word Imagery Effects on Explicit and Implicit Memory. Nicholas Bube, Drew Finke, Darcy Lemon, and Meaghan Topper.
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Nicholas Bube, Drew Finke,
Darcy Lemon, and Meaghan Topper
Memory research has primarily focused on the distinction between implicit and explicit memory. The most pressing question now is whether or not these two types of long-term memory are maintained by different brain systems. Researchers in favor of this distinction have used ERP data to support their claims.
Reasons for Further Study between implicit and explicit memory. The most pressing question now is whether or not these two types of long-term memory are maintained by different brain systems. Researchers in favor of this distinction have used ERP data to support their claims. Many of the previous experiments found that low frequency words are more likely than high frequency words to be recalled using the explicit memory system. This may occur because low frequency words are more distinct and are therefore easier to remember. In much the same manner, we propose that high imagery words will be easier to recall than low imagery words because they elicit a visual representation. High imagery words are, therefore, more likely to be recalled using the explicit memory system, while low imagery words use the implicit memory system. Previous experiments did not analyze data spatially within the brain, only temporally. This experiment makes use of both of these methods in order to provide for a better data analysis.
Spatial Analysis between implicit and explicit memory. The most pressing question now is whether or not these two types of long-term memory are maintained by different brain systems. Researchers in favor of this distinction have used ERP data to support their claims.
Examination of spatial data reveals that brain activity did not differ significantly when comparing high to low imagery words, and differed only slightly between the Remember and Know responses (Figure 1).
Overall brain activity was observed to increase during the 300-500 ms time frame in the frontal and right temporal lobes (Figure 2).
ERPs recorded for the Remember response in the 300-700 ms time frame are consistently more intense for high imagery words than low throughout all areas of the brain (Figure 3).
ERPs recorded for the Remember and Know responses, although differing in intensity, exhibit waveforms of nearly identical shape in most regions of the brain (Figure 4).Results and Data Analysis
Both spatial and temporal aspects of the ERP data obtained for this experiment were examined for evidence of separate brain systems at work in explicit and implicit memory processes.
The data in this study provides neither strong evidence that implicit and explicit memory occupy different brain systems, nor proof that high imagery words are recalled using the explicit memory system and low imagery words using the implicit memory system. When examining spatial activity data, little variation is seen, and there is very little evidence to suggest the existence of separate implicit and explicit memory systems. Temporal ERP data showed that high imagery words elicited a stronger, more positive Remember response than low imagery words, suggesting that high imagery words may be more strongly remembered. One further related observation of the data was that the waveforms of the Remember and Know responses differed significantly in their potentials within the 200-600 ms time frame, but were nearly identical in the shape of the waveforms. The temporal data paired with the spatial data suggest that implicit and explicit memory occupy the same regions within the brain, but that these areas of the brain are more highly activated during explicit recollection.
It is possible that implicit and explicit memory do not differ during recall, but differ greatly in encoding. Perhaps it is the way that memory is stored and not the manner by which it is retrieved that is the important difference between the two types of memory. Because ERPs were not recorded during encoding, however, a conclusion of this sort can not be drawn.
Note: Numbers above images refer to time elapsed after presentation of stimulus (in milliseconds).
Overall Activity: Remember
Overall Activity: Know
Figure 3. Temporal ERP Data Demonstrating Increased Signal Intensity for High vs. Low Imagery Words
Note: Plots show Potential (V) vs. Time (ms) data for recorded ERPs at various areas of the brain
Figure 4. Remember vs. Know Comparison of ERP Waveforms in Various Regions of the Brain