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The role of sleep in the consolidation of auditory input A scientific literature review

The role of sleep in the consolidation of auditory input A scientific literature review

Erwin Blanco San MartĂ­n

This paper has been designed and compiled as a pre requisite to pass the Integrated advanced communicative competences of English language, September 2013.

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The role of sleep in the consolidation of auditory input A scientific literature review Introduction

Since the very moment we hear a sound we can discriminate whether it is human speech or a tone, and also it is possible to identify whether it is new or already known. What is the internal functioning of the auditory cortex? , Does the sleep play any role in memorizing new auditory information? Do we share the same memory systems to store any event or knowledge? To start off we might first take a glance at the scientific knowledge about brain anatomy. The theory of multiple memory systems was based a long time on behavioral experiments without a biological support reinforcing the findings. Packard, M. G., Hirsh, R., & White, N. M. (1989) developed a reliable research based on experimental tests to prove the existence of anatomically distinct memory systems. The experiments consisted on selecting two groups of rats to which different kind of brain lesions were applied, the first type involved deep fimbria-fornix (hippocampus region) damage and the second involved disruptive lesions in the caudate area. The tests consisted of a win-stay radial maze designed to probe the long term memory of rats in getting food and a win-shift radial maze intended to probe the working memory. A third group of rats was added in order establish a control sample, the results were as follows: In the win-stay test the rats impaired at caudate nucleus visited the arms more times than the fornix and control group, in addition the fornix group was the fastest in memorizing and getting the food. On the other hand, in the win-shift maze, the fornix group had the highest score of errors in comparison with the control and caudate groups.

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The role of sleep in the consolidation of auditory input A scientific literature review It can be drawn as a result that at mammals are endowed with at least two kinds of memory systems and that are related to both specific parts of the brain and to specific abilities.

When we first learned a new word by ear -without reading-, how much does it take to integrate it in our mental lexicon?

Dumay, N., & Gaskell, M. G. (2007) taking

advantage of the theory that states that during auditory word recognition the phonologically-close words compete to be retrieved from our mental lexicon (Gaskell, M. G., & Dumay, N., 2003), conducted a research to measure the word-competition effect across different time lapses, including sleep periods. The experiment consisted of 25 male English speakers divided into 2 groups. Each group learned word series consisting of a known word and two phonologically similar competitors, for instance: Cathedral followed by cathedruce and cathedruke. Immediately after the test, then 12 and 24 hours after, the participants took a word free recall test and a recognition test. The results evidenced a similar performance in both groups at the first test, conversely 12 hours after; the PM group (Who slept) outperformed far in latency of response and word recall tests in comparison to the AM group. The explanation for the results accounts for an enhanced consolidation as a result of the sleeping period for the PM

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The role of sleep in the consolidation of auditory input A scientific literature review group, finding that is reinforced by other studies based on the consolidating effect of sleep in word recall (Plihal & Born (1997). Furthermore 24 hours after, the score of both tests were almost even, why? Because at that point both groups had already had a sleeping period that resulted into effective consolidation.

Comparable results registered a research aiming at measuring the influence of sleep on auditory learning conducted by Gaab, N., Paetzold, M., Becker, M., Walker, M. P., & Schlaug, G. (2004). The method consisted on exposing subjects to sine wave tones spanning from 41-64 Hz. Those subjects that had a sleep period after the experiment shown an increased enhancement in tone recognition in comparison to the group that experienced a lapse of wakefulness, however the former group improved almost up to the same level of the sleeping group after the natural sleeping period when tested one day after. In conclusion regardless to the hour of learning the sleeping process will benefit with consolidation to either group.

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The role of sleep in the consolidation of auditory input A scientific literature review It is clear according to the overwhelming evidence mentioned before that the human memory system is divided into other subsystems that underlie to the classic differentiation of declarative and non declarative memory (Squire, L.R., 1987)

Knowing that sleep has a substantial role in the acquisition and codification of auditory lexicon the question that remains is: What is the algorithm that the auditory cortex executes when matching and auditory stimulus with a lexicalized auditory element?, Goldinger, (1996) conducted a complex investigation where around 100 university students were exposed to spoken words uttered by different voices. The results can be synthesized in these findings: First the auditory cortex is able to divide meaning and voice details such as frecuency, (Purves, D., Augustine, G. J., Fitzpatrick, D., Katz, L. C., LaMantia, A. S., McNamara, J. O., & Williams, S. M , 2001), second, the episodic memory is able to retain surface details such tone and pitch, third, that in word recognition the subjects were able to identify the already learned words versus new ones even in presence of noise. An important

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The role of sleep in the consolidation of auditory input A scientific literature review variable to point out is that the less voices they heard, the more words they recognized in long terms test.

The human auditory cortex. (A) Diagram showing the brain in left lateral view, including the depths of the lateral sulcus, where part of the auditory cortex occupying the superior temporal gyrus normally lies hidden. The primary auditory cortex (A1) is shown in blue; the surrounding belt areas of the auditory cortex are in red. (B) The primary auditory cortex has a tonotopic organization, as shown in this blowup diagram of a segment of A1.Purves, Dale. "The Human Auditory Cortex." Sinauer Associates. U.S. National Library of Medicine, 18 Jan. 0000. Web. 15 Sept. 2013

Further than the conceptual certainty that sleep is crucial for auditory consolidation, the last question that remains is what bio-electro-chemical changes does sleep trigger in order to consolidate new information?, Cantero, J. L., Atienza, M., Salas, R. M., & Dominguez-Marin, E. (2002), investigated changes in the brain electrical activity patterns during human sleep after a long period of continuous auditory stimulation. The aim of the research was to asses any modification in the electrical activity (recorded by EEG) as result of a prolonged auditory input during previous wakefulness. The sample to apply the experiment consisted of eight volunteer subjects that were exposed to 4 different auditory patterns for 6 hours in different frequencies, ranging from 300Hz to 8000Hz, in order to 6


The role of sleep in the consolidation of auditory input A scientific literature review ensure the activation of different neuronal groups in the auditory cortex. The subjects were equipped with EEG electrodes to measure electrophysiological changes during sleep.

The results of the experiment presented a massive calcium entry provoked by the excitation–inhibition input patterns (See image below), an increased spectral power and larger wave amplitude during SWS sleep in those regions that are related to auditory input and processing, namely, temporal cortex and parietal cortex, however it was disclosed that stimulation over the left ear did not correlate coherently with an enhanced activity in the right brain hemisphere, it could be due to the different capacities of the hemispheres in processing the sounds and speech (Sapher & Levanthal 1978) & (Van Lancker & kreiman, 1978). No changes were noticed during REM sleep period. Considering the variations of electrical patterns there are two explanations that account for this surplus of spectral power and wave amplitude: The first accounts for a homeostatic response due to overstimulation of auditory neural networks, the second, stands for a novel experience-dependant cortical reorganization (learning process). In either cases SWS is a critical for such synaptic reorganization, in addition the former explanation might also rely on the first to thrive.

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The role of sleep in the consolidation of auditory input A scientific literature review As a brief synthesis of the state of the art in the role of sleep in the consolidation of auditory input, it is possible to assert that mammals are endowed with different anatomical and functional memory systems, also that the sleep plays a key role in the acquisition of new auditory lexical items that are integrated during SWS sleep period. Regarding to physiological changes, it has been clear that the SWS sleep involves surplus of electrical activity and a homeostatic release of neurotransmitters (Calcium, CA2+) nevertheless this cortical reorganization is only triggered by previous auditory-cortex overstimulation.

Extension: 1.150 words, without considering image footers and references.

References

Cantero, J. L., Atienza, M., Salas, R. M., & Dominguez-Marin, E. (2002). Effects of prolonged waking-auditory stimulation on electroencephalogram synchronization and cortical coherence during subsequent slow-wave sleep.The Journal of neuroscience, 22(11), 4702-4708.

Dumay, N., & Gaskell, M. G. (2007). Sleep-associated changes in the mental representation of spoken words. Psychological Science, 18(1), 35-39.

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The role of sleep in the consolidation of auditory input A scientific literature review Gaab, N., Paetzold, M., Becker, M., Walker, M. P., & Schlaug, G. (2004). The influence of sleep on auditory learning: a behavioral study. Neuroreport, 15(4), 731-734.

Gaskell, M. G., & Dumay, N. (2003). Lexical competition and the acquisition of novel words. Cognition, 89(2), 105-132.

Goldinger, S. D. (1996). Words and voices: episodic traces in spoken word identification and recognition memory. Journal of Experimental Psychology: Learning, Memory, and Cognition, 22(5), 1166.

Packard, M. G., Hirsh, R., & White, N. M. (1989). Differential effects of fornix and caudate nucleus lesions on two radial maze tasks: evidence for multiple memory systems. The Journal of neuroscience, 9(5), 1465-1472.

Plihal, W., & Born, J. (1997). Effects of early and late nocturnal sleep on declarative and procedural memory. Journal of Cognitive Neuroscience, 9(4), 534-547.

Purves, D., Augustine, G. J., Fitzpatrick, D., Katz, L. C., LaMantia, A. S., McNamara, J. O., & Williams, S. M. (2001). The auditory system.

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The role of sleep in the consolidation of auditory input A scientific literature review Safer, M. A., & Leventhal, H. (1977). Ear differences in evaluating emotional tones of voice and verbal content. Journal of Experimental Psychology: Human Perception and Performance, 3(1), 75.

Squire, L. R. (1987). Memory and brain. Oxford University Press.

Van Lancker, D., & Kreiman, J. (1987). Voice discrimination and recognition are separate abilities. Neuropsychologia, 25(5), 829-834.

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