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Age-related changes in motor cortical representation and interhemispheric interactions: a transcranial magnetic stimulation study.

Coppi E, Houdayer E, Chieffo R, Spagnolo F, Inuggi A, Straffi L, Comi G, Leocani L - Front Aging Neurosci (2014)

Bottom Line: The APB map of the right hemisphere was reduced in the older group compared to the younger (p = 0.021).The reduction of right ISP area correlated significantly with the worsening of motor performances.The decreased ISP and increased frequency of MM suggest a reduction of transcallosal inhibition.

View Article: PubMed Central - PubMed

Affiliation: Neurological Department and Experimental Neurophysiology Unit, Institute of Experimental Neurology (INSPE), University Hospital-IRCCS San Raffaele , Milan , Italy.

ABSTRACT
To better understand the physiological mechanisms responsible for the differential motor cortex functioning in aging, we used transcranial magnetic stimulation to investigate interhemispheric interactions and cortical representation of hand muscles in the early phase of physiological aging, correlating these data with participants' motor abilities. Right-handed healthy subjects were divided into a younger group (n = 15, mean age 25.4 ± 1.9 years old) and an older group (n = 16, mean age 61.1 ± 5.1 years old). Activity of the bilateral abductor pollicis brevis (APB) and abductor digiti minimi (ADM) was recorded. Ipsilateral silent period (ISP) was measured in both APBs. Cortical maps of APB and ADM were measured bilaterally. Mirror movements (MM) were recorded during thumb abductions. Motor abilities were tested using Nine Hole Peg Test, finger tapping, and grip strength. ISP was reduced in the older group on both sides, in terms of duration (p = 0.025), onset (p = 0.029), and area (p = 0.008). Resting motor threshold did not differ between groups. APB and ADM maps were symmetrical in the younger group, but were reduced on the right compared to the left hemisphere in the older group (p = 0.008). The APB map of the right hemisphere was reduced in the older group compared to the younger (p = 0.021). Older subjects showed higher frequency of MM and worse motor abilities (p < 0.001). The reduction of right ISP area correlated significantly with the worsening of motor performances. Our results showed decreased interhemispheric interactions in the early processes of physiological aging and decreased cortical muscles representation over the non-dominant hemisphere. The decreased ISP and increased frequency of MM suggest a reduction of transcallosal inhibition. These data demonstrate that early processes of normal aging are marked by a dissociation of motor cortices, characterized, at least, by a decline of the non-dominant hemisphere, reinforcing the hypothesis of the right hemi-aging model.

No MeSH data available.


Related in: MedlinePlus

Ipsilateral silent period parameters (duration, area, and onset) according to group and side (average ± SD). L-Hem, left hemisphere; R-Hem, right hemisphere. *p < 0.05. Examples of ISP traces in one older and one younger subject are exposed on the lower part of the figure.
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Figure 1: Ipsilateral silent period parameters (duration, area, and onset) according to group and side (average ± SD). L-Hem, left hemisphere; R-Hem, right hemisphere. *p < 0.05. Examples of ISP traces in one older and one younger subject are exposed on the lower part of the figure.

Mentions: The ANOVA for repeated measures showed a significant SIDE effect (F1,18 = 9.841; p = 0.006) and a significant GROUP effect (F1,18 = 5.614; p = 0.029) for the ISPonset (one upper outlier for right ISPonset in the older group and two lower outliers for right ISPonset in the older group). ISPduration showed a significant SIDE effect (F1,21 = 5.047; p = 0.036) as well as a significant GROUP effect (F1,21 = 5.798; p = 0.025). In ISParea analyses, the ANOVA demonstrated also a significant GROUP effect (F1,19 = 8.82; p = 0.008), and a trend for a SIDE effect (F1,19 = 3.567; p = 0.074) (one upper outlier for right ISParea in the older group and one lower outlier for right ISParea in the younger group). Thus, in the older group ISPonset was delayed, ISPduration and ISParea were reduced on both sides (see Figure 1). Moreover, in both groups, left hand ISP was significantly greater than right hand ISP (except for ISParea where only a trend was observed). It is noteworthy that pre-trigger EMG levels were similar in both groups (p > 0.05). ISP data are presented in Table 1.


Age-related changes in motor cortical representation and interhemispheric interactions: a transcranial magnetic stimulation study.

Coppi E, Houdayer E, Chieffo R, Spagnolo F, Inuggi A, Straffi L, Comi G, Leocani L - Front Aging Neurosci (2014)

Ipsilateral silent period parameters (duration, area, and onset) according to group and side (average ± SD). L-Hem, left hemisphere; R-Hem, right hemisphere. *p < 0.05. Examples of ISP traces in one older and one younger subject are exposed on the lower part of the figure.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4128298&req=5

Figure 1: Ipsilateral silent period parameters (duration, area, and onset) according to group and side (average ± SD). L-Hem, left hemisphere; R-Hem, right hemisphere. *p < 0.05. Examples of ISP traces in one older and one younger subject are exposed on the lower part of the figure.
Mentions: The ANOVA for repeated measures showed a significant SIDE effect (F1,18 = 9.841; p = 0.006) and a significant GROUP effect (F1,18 = 5.614; p = 0.029) for the ISPonset (one upper outlier for right ISPonset in the older group and two lower outliers for right ISPonset in the older group). ISPduration showed a significant SIDE effect (F1,21 = 5.047; p = 0.036) as well as a significant GROUP effect (F1,21 = 5.798; p = 0.025). In ISParea analyses, the ANOVA demonstrated also a significant GROUP effect (F1,19 = 8.82; p = 0.008), and a trend for a SIDE effect (F1,19 = 3.567; p = 0.074) (one upper outlier for right ISParea in the older group and one lower outlier for right ISParea in the younger group). Thus, in the older group ISPonset was delayed, ISPduration and ISParea were reduced on both sides (see Figure 1). Moreover, in both groups, left hand ISP was significantly greater than right hand ISP (except for ISParea where only a trend was observed). It is noteworthy that pre-trigger EMG levels were similar in both groups (p > 0.05). ISP data are presented in Table 1.

Bottom Line: The APB map of the right hemisphere was reduced in the older group compared to the younger (p = 0.021).The reduction of right ISP area correlated significantly with the worsening of motor performances.The decreased ISP and increased frequency of MM suggest a reduction of transcallosal inhibition.

View Article: PubMed Central - PubMed

Affiliation: Neurological Department and Experimental Neurophysiology Unit, Institute of Experimental Neurology (INSPE), University Hospital-IRCCS San Raffaele , Milan , Italy.

ABSTRACT
To better understand the physiological mechanisms responsible for the differential motor cortex functioning in aging, we used transcranial magnetic stimulation to investigate interhemispheric interactions and cortical representation of hand muscles in the early phase of physiological aging, correlating these data with participants' motor abilities. Right-handed healthy subjects were divided into a younger group (n = 15, mean age 25.4 ± 1.9 years old) and an older group (n = 16, mean age 61.1 ± 5.1 years old). Activity of the bilateral abductor pollicis brevis (APB) and abductor digiti minimi (ADM) was recorded. Ipsilateral silent period (ISP) was measured in both APBs. Cortical maps of APB and ADM were measured bilaterally. Mirror movements (MM) were recorded during thumb abductions. Motor abilities were tested using Nine Hole Peg Test, finger tapping, and grip strength. ISP was reduced in the older group on both sides, in terms of duration (p = 0.025), onset (p = 0.029), and area (p = 0.008). Resting motor threshold did not differ between groups. APB and ADM maps were symmetrical in the younger group, but were reduced on the right compared to the left hemisphere in the older group (p = 0.008). The APB map of the right hemisphere was reduced in the older group compared to the younger (p = 0.021). Older subjects showed higher frequency of MM and worse motor abilities (p < 0.001). The reduction of right ISP area correlated significantly with the worsening of motor performances. Our results showed decreased interhemispheric interactions in the early processes of physiological aging and decreased cortical muscles representation over the non-dominant hemisphere. The decreased ISP and increased frequency of MM suggest a reduction of transcallosal inhibition. These data demonstrate that early processes of normal aging are marked by a dissociation of motor cortices, characterized, at least, by a decline of the non-dominant hemisphere, reinforcing the hypothesis of the right hemi-aging model.

No MeSH data available.


Related in: MedlinePlus