Research - Clinical - Cognitive Function

Cognitive Function

Conflicting effects of RFR exposure on cognitive function have been reported. Several studies have demonstrated improved cognitive function in volunteers exposed to RF radiation in the frequency range of cell phones. In Preece's study (1999), of fifteen different tests on volunteers exposed to a 915 MHz signal from a phone model, one test showed results that were marginally different in the exposed compared with the controls. The authors speculated that the effect might be due to a localized heating effect. Koivisto (2000a) found that volunteers exposed to RF fields at 902 MHz had faster response times in 3 out of a total of 12 tasks. In another study, these authors (2000b) reported that exposure to 902 MHz was associated with accelerated performance of memory tasks by their study subjects. However, the authors did not think that the results were of any practical significance. A slight temperature rise in brain tissue was again suggested as a possible mechanism. The same group replicated their study, with improved methodology, and failed to show any effect of RF radiation on cognitive function (Haarala, 2003). The authors also repeated their study on short-term memory, but with improvements in the methodology, and failed to show any effect (Haarala, 2004). Jech (2001) also found a decrease in reaction time, in response to target stimuli. This occurred in a group of people with narcolepsy studied during exposure to 900 MHz at a SAR of 0.06W/kg for 45 minutes. Curcio (2004) reported an improvement in reaction times that was time-dependent. An interval of 25-30 minutes of EMF exposure was needed to observe the changes. No effects were seen in cognitive and attentional tasks. Edelstyn (2002) reported that performance was facilitated in two tests of attentional capacity and one of processing speed in subjects exposed to 900 MHz for 15 minutes. Lass and colleagues (2002) found a significant increase in variance of errors in two tasks of attention and short-term memory in subjects exposed to a 7-Hz modulated 450 MHz field. However, they found a decrease in errors in the exposed group in a third task, said to be less difficult than the other two. Smythe and Costall (2003) reported that mobile phone use facilitated memory in male, but not female, subjects, but the number of subjects was small, and the results were not consistent. Lee and colleagues (2003) found a decrease in reaction time in one of two tasks, but only when the task was repeated with the 1900 MHz phone switched off. There was no difference in the other task or in the number of correct responses. Zwamborn (2003) reported alterations in the speed of response in several tests of brain function in subjects exposed to weak GMS and UMTS-like fields. The results were not consistent. Reaction time increased slightly compared with baseline, while there was a decrease in time in response to the other tests used. Also, the changes were seen in some but not all of the frequencies tested. Eliyahu (2006) found that in right-handed males, response times were slowed when the subjects used their left hand while exposed to RFR to their left hemisphere. Regel (2007) reported that exposure to pulse-modulated RFR at 900 MHz for 30 minutes reduced reaction time and increased accuracy in a working-memory task.

Other studies have found no effects. Besset (2005) found that exposure to mobile phone RFR for 2 hours a day for 27 days had no effect on cognitive function. Schmid (2005) found no effect on visual perception when volunteers were exposed to 1970 MHz RFR during the tests. Preece (2005) and Haarala (2005) could not find any effect of mobile phone transmission on the cognitive function of children aged 10-14 years. Other combinations of handedness and exposure side did not produce this response. Russo (2006) attempted to overcome the deficiencies in many of the above studies i.e. the small sample sizes (and reduced statistical power), and the lack of double blinding. These authors found no effects of RF exposure on cognitive tasks, whether the RF signal was GSM or CW, or whether the phone was positioned on the left ear or on the right. Fritzer (2007), in a randomized, blinded experiment in young adults, reported no effects on neurocognitive testing with exposure to 900 MHz RFR overnight for 6 consecutive nights. The testing was done on the 2nd and 6th nights. Haarala (2007) found no effects on cognitive tasks in subjects tested while exposed to either continuous wave (CW) or pulse-modulated (PM) RFR at 902 MHz, with each hemisphere being exposed in turn. This latter group also found no effects on performance of an auditory and a visual memory task in a similar experiment, using both CW and PM RFR exposure (Krause, 2007). Cinel (2007) reported no effect on an auditory threshold task of RFR at 900 MHz and SAR of 1.4 W/kg.

Another study by Kolodynski (1996) discussed cognitive function in schoolchildren living in the area of a radio location station, in which the radiofrequencies used are very different from that used in mobile phones.

Ferreri (2006) used Transcranial Magnetic Stimulation to measure human brain excitability, and found that RFR from a GSM phone modified brain excitability.

Huber (2002) showed increased cerebral blood flow on the same side as exposure to pulse-modulated 900 MHz radiation, as compared with sham exposure. The same authors reported similar findings in another study, and commented that the observed changes could be related specifically to the pulse-modulation (Huber, 2005). Haarala (2003), however, found decreased blood flow at a site remote from the maximum RF field. They attributed this to an auditory signal from the mobile phone, not to the EMF from the phone. The latter study was different from Huber's, in that the subjects performed memory tasks while being exposed to the RF field, and the blood flow measurements were done at the same time as the exposure took place. In Huber's study the blood flow was measured 10 minutes after the exposure. Haarala and colleagues (Aalto 2006), in a double-blind and counterbalanced study, exposed 12 volunteers to RFR at 902 MHz frequency. They recorded blood flow by PET scanning while the subjects performed a memory task. They found that cerebral blood flow was decreased in the inferior temporal cortex beneath the antenna of the phone and more distantly in the prefrontal cortex. They attributed this to increased neuronal activity induced by the electromagnetic fields.

Khiat (2006) used proton magnetic resonance spectroscopy to measure metabolites in different areas of the brain. They did not find any differences between heavy users of cell phones and non-users, or between the ipsilateral and contralateral sides of the brain in cell phone users.

In a review of behavioural and cognitive effects of microwave exposure, D'Andrea, Adair, and Lorge (2003) state: "At the present time, the evidence that RFR exposure from mobile phone use can influence cognitive performance is very weak."

In another review D'Andrea, Chou, Johnstone, and Adair (2003) agree with this general conclusion. They point out that the failure of one group to replicate their findings (Koivisto 2000a, Haarala 2003) is significant. The other studies suffer from problems in design that include:

The effects on function are seen with only a small number of tasks
The authors failed to use the appropriate statistical corrections for the multiple comparisons they performed
There was often a lack of validation of the cognitive tests that were used
Lack of replication of the findings

Cook, Saucier, Thomas, and Prato (2006), in a review of papers published between 2001 and 2005, conclude that the effect of mobile phones on various performance measures are more equivocal than physiological measures, such as EEG. Effect sizes are small, and Cook et al. suggest several possible explanations for this:

Physiological effects may be superfluous and result in no behaviours change
Behavioural measures may not be sensitive enough to detect changes in brain function
Neglecting to continue measuring into the post-exposure period may make it difficult to interpret the data
The lack of significant performance effects may be due to small sample size
• The performance tests may not be adequate to demonstrate subtle effects
Laterality of EMF exposure may make a difference
Some studies suggest that there may be differences in responses between males and females

These authors suggest that the most promising technical development is the integration of bioelectromagnetics with functional imaging.

Haarala and colleagues (2007) also point out that methodology has varied considerably from study to study. The designs have been within-subjects and others between-subjects; or single-blind versus double-blind; or relatively controlled exposure unit positioning to a rather questionable one. The power used has also varied, as has the laterality of exposure and the type of exposure (continuous wave or pulse modulation).

References:

Authors
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Title
Mobile phone affects cerebral blood flow in humans.
Journal
J Cereb Blood Flow Metab 2006;26:885-890.
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Authors
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Principal component analysis of the P600 waveform: RF and gender effects.
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Neurosci Lett. Apr 29, 2010 Ahead of print.

Authors
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Title
Comments on neurophysiological effects of mobile phone electromagnetic fields on humans: A comprehensive review
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BioelectromagneticsAhead of Print 28 December 2007 10.1002/bem.20397

Authors
Besset A, Espa F, Dauvilliers Y, Billiard M, et al.
Title
No effect on cognitive function from daily mobile phone use.
Journal
Bioelectromagnetics 2005;26:102-108.
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Authors
Carrubba S, Frilot C 2nd, Chesson AL Jr, Marino AA.
Title
Mobile-phone pulse triggers evoked potentials.
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Neurosci Lett. Dec 3, 2009. Ahead of print.

Authors
Cinel C, Boldini A, Russo R, Fox E.
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Bioelectromagnetics 2007;28:493-496.
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Authors
Curcio G, Ferrara M, de Gennaro L, Cristiani R, et al.
Title
Time-course of electromagnetic field effects on human performance and tympanic temperature
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Authors
Curcio G, Valentini E
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Bioelectromagnetics Ahead of print 13 February 2008 10.1002/bem.20398.

Authors
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Authors
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Journal
J Cereb Blood Flow Metab. Feb 25, 2009. Ahead of print.

Authors
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Hypersensitivity to RF fields emitted from CDMA cellular phones: A provocation study.
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Bioelectromagnetics. Jun 23, 2009 Ahead of print.

Authors
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Authors
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Title
The acute effects of exposure to the electromagnetic field emitted by mobile phones on human attention.
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Neuroreport 2002;13:119-121
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Authors
Eliyahu I, Luria R, Hareuveny R, Margaliot M, et al.
Title
Effects of radiofrequency radiation emitted by cellular telephones on the cognitive function of humans.
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Authors
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Title
Short-term exposure to mobile phone base station signals does not affect cognitive functioning or physiological measures in individuals who report sensitivity to electromagnetic fields and controls.
Journal
Bioelectromagnetics. May 27, 2009. Ahead of print.

Authors
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Title
Mobile phone emissions and human brain excitability.
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Ann Neurol 2006;60:188-196.
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Authors
Fritzer G, Goder R, Friege L, Wachter J et al.
Title
Effects of short- and long-term pulsed radiofrequency electromagnetic fields on night sleep and cognitive functions in healthy subjects.
Journal
Biolectromagnetics 2007;28:316-325.
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Authors
Haarala C, Bjornberg L, Ek M, Laine M, et al.
Title
Effect of 902 MHz electromagnetic field emitted by mobile phones on human cognitive function: A replication study.
Journal
Bioelectromagnetics 2003;24:283-288.
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Authors
Haarala C, Aalto S, Hautzel H, Julkunen L, et al.
Title
Effects of a 902 MHz mobile phone on cerebral blood flow in humans: A PET study.
Journal
NeuroReport 2003;14:2019-2023.
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Authors:
Haarala C, Ek M, Bjornberg L, Laine M, et al.
Title:
902 MHz mobile phone does not affect short term memory in humans.
Journal:
Bioelectromagnetics 2004;25:452-456.
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Authors
Haarala C, Bergman M, Laine M, Revonsuo A, et al.
Title
Electromagnetic field emitted by 902 MHz mobile phones shows no effect on children's cognitive function.
Journal
Bioelectromagnetics 2005; 26, issue S7:S144-150.
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Authors
Haarala C, Takio F, Rintree T, Lainie M, et al.
Title
Pulsed and continuous wave mobile phone exposure over left versus right hemisphere: Effects on human cognitive function.
Journal
Biolectromagnetics 2007;28: 289-295.
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Authors
Huber R, Treyer V, Borbely AA, Schuderer J, et al.
Title
Electromagnetic fields, such as those from mobile phones, alter regional cerebral blood flow and sleep and waking EEG.
Journal
J Sleep Res 2002;11:289-235.
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Authors
Huber R, Treyer V, Schuderer J, Berthold T, Buck A, et al.
Title
Exposure to pulse-modulated radio frequency electromagnetic fields affects regional blood flow.
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Eur J Neurosci 2005;21:1000-6.
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Authors
Jech R, Sonka K, Ruzicka E, Nebuzelsky, et al.
Title
Electromagnetic field of mobile phone affects visual event related potential in patients with narcolepsy.
Journal
Bioelectromagnetics 2001;22:519-528.
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Authors
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Authors
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Title
Monitoring the effect of mobile phone use on the brain by proton magnetic resonance spectroscopy.
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Int J Radiat Biol 2006;82:681-685.
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Authors
Kleinlogel H, Dierks Th, Koenig Th, Lehmann H, Minder A, Berz R.
Title
Effects of weak mobile phone -Electromagnetic fields (GSM, UMTS) on event related potentials and cognitive functions.
Journal
Bioelectromagnetics 2008 Apr 17 Ahead of print.

Authors
Koivisto M, Revonsvo A, Krause C, Haarola C, Sillanmaki L, Laine M, Hamalainen H.
Title
Effects of 902 MHz electromagnetic fields emitted by cellular telephones on response times in humans.
Journal
Neuroreport 2000a; 11:413 - 415
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Authors
Koivisto M, Krause CM, Revonsuo A, et al.
Title
The effects of electromagnetic field emitted by GSM phones on working memory
Journal
NeuroReport 2000b;11:1641-1643.
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Author:
Kolodynski AA, Kolodynska VV.
Title:
Motor and psychological functions of school children living in the area of the Skrunda Radio Location Station in Latvia.
Journal:
The Science of the Total Environment 1996;180:87-93.
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Authors
Krause CM, Pesonen M, Bjornberg C Haarala, Hamalainen H.
Effects of pulsed and continuous wave 902 MHz mobile phone exposure on brain oscillatory activity during cognitive processing.
Journal
Bioelectromagnetics 2007;28:296-308.
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Authors
Lass J, Tuulik V, Ferenets R, Riisalo R, et al
Title
Effects of 7 Hz-modulated 450 MHz electromagnetic radiation on human performance in visual memory tasks.
Journal
Int J Radiat Biol 2002;78:937-944.
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Authors
Lee TMC, Lam P-K, Lee LTS, Chan CCH.
Title
The effect of the duration of exposure to the electromagnetic field emitted by mobile phones on human attention.
Journal
NeuroReport 2003;14:1361-1364.
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Authors
Luria R, Eliyahu I, Hareuveny R, Margaliot M, Meiran N.
Title
Cognitive effects of radiation emitted by cellular phones: The influence of exposure side and time.
Journal
Bioelectromagnetics. Ahead of print November 17, 2008. DOI 10.1002/bem.20458.

Authors
Mizuno Y, Moriguchi Y, Hikage T, Terao Y, Ohnishi T, Nojima T, Ugawa Y.
Title
Effects of W-CDMA 1950 MHz emitted by mobile phones on regional cerebral blood flow in humans.
Journal
BioelectromagneticsMay 27, 2009. Ahead of print.

Authors
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Title
Cognitive impairment in rats after long-term exposure to GSM-900 mobile phone radiation.
Journal
Bioelectromagnetics 2008; 29(3):219-232.

Authors
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Title
The effect of electromagnetic field emitted by a mobile phone on the inhibitory control of saccades.
Journal
Clin Neurophysiol. Jan 16, 2010 Ahead of print.

Authors:
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Title:
Effect of a 915-MHz simulated mobile phone signal on cognitive function in man.
Journal:
International Journal of Radiation Biology 1999;75:447-456.
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Authors
Preece AW, Goodfellow S, Wright MG, Butler SR, et al.
Title
Effect of 902 MHz mobile phone transmission on cognitive function in children.
Journal
Bioelectromagnetics 2005; 26, issue S7:S138-143.
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Authors
Riddervold IS, Pedersen GF, Andersen NT, Pedersen AD, Andersen JB, Zachariae R, Mølhave L, Sigsgaard T, Kjærgaard SK.
Title
Cognitive function and symptoms in adults and adolescents in relation to rf radiation from UMTS base stations.
Journal
Bioelectromagnetics 2008;29(4);257-267.

Authors
Riddervold IS, Kjærgaard SK, Pedersen GF, Andersen NT, Franek O, Pedersen AD, Sigsgaard T, Zachariae R, Mølhave L, Andersen JB.
Title
No effect of TETRA hand portable transmission signals on human cognitive function and symptoms.
Journal
Bioelectromagnetics. March 8, 2010. Ahead of print.

Authors
Regel S, Gottselig, J, Schuderr, J, Tinguely, G, et al.
Title
Pulsed radio frequency radiation affects cognitive performance and the waking electroencephalogram. Journal
Neuroreport 2007;18:803-807.
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Authors
Russo R, Fox E, Cinel C, Boldini A, et al.
Title
Does acute exposure to mobile phones affect human attention?
Journal
Bioelectromagnetics 2006;27:215-220.
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Authors:
Schmid G, Sauter C, Stepansky R, Lobentanz IS, et al.
Title:
No influence on selected parameters of human visual perception of 1970 MHz UMTS-like exposure.
Journal:
Bioelectromagnetics 2005;243-250.
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Authors:
Söderqvist F, Hardell L, Carlberg M, Mild KH.
Title:
Radiofrequency Fields, Transthyretin, and Alzheimer's Disease.
Journal:
J Alzheimers Dis. Feb 17, 2010. Ahead of print.

Authors:
Smythe JW, Costall B.
Title:
Mobile phone use facilitates memory in male, but not female, subjects.
Journal:
NeuroReport 2003;14:243-246.
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Authors:
Soderqvist F, Carlberg M, Mild KH, Hardell L.
Title:
Exposure to a 890MHz mobile phone-like signal and serum levels of S100B and transthyretin in volunteers.
Journal:
Toxicological Letters. May 7 2009 Ahead of print.

Authors:
Unterlechner M, Sauter C, Schimd G, Zeithofer J.
Title:
No effect of an UMTS mobile-like electromagnetic fields of 1.97 GHz on human attention and reaction time.
Journal:
Bioelectromagnetics 2008;29:145-153.

Authors:
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Title:
Mobile phone exposure and spatial memory.
Journal:
Bioelectromagnetics Ahead of print 15 Sep 2008.

Authors:
Zwamborn APM, Vossen SHJA, van Leersum BJAM, Ouwens MA, Makel WN, for the Netherlands Organisation for Applied Scientific Research (TNO).
Title
Effects of global communication system radio-frequency fields on well being and cognitive functions of human subjects with and without subjective complaints.
Journal:
TNO-report (2003). FEL-03-C148
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