Cross Laterality: Handedness, Footedness and Foot overlapping

 

Susie Jeyalyn David^1*, Dr. W.M.S. Johnson²

¹Ph.D Scholar, Department of Medical Sciences, Bharath University, Selaiyur, Chennai–600073, India.

²Faculty and Head Anatomy, Department of Medical Sciences, Sree Balaji Medical College, Chromepet, Chennai-600044 India.

 

ABSTRACT:

Lateralisation is the preference or dominance of one side of the body or an organ over the other side. The marker of laterality is handedness. Most of the population is right handed due to the left cerebral dominance whereas only 10% of population is left handed. The study of cerebral lateralization involves identifying the key reliable predictors to analyse the exact behavioural manifestations actuated by the lateral hemispheres. Though the analogue factor of using the preferred hand has been widely used as the predictor, footedness could also be yet another dimension of analysing the laterality behaviour of cerebral hemispheres especially among the left handed population. In human beings, the establishment of motor system pursue the basic principle of control of distal movements contralaterally. This principle is reflected at the anatomical level in virtually complete crossing of corticospinal fibres which innervate distal muscles.This work focusses on the analysis of preference of foot over the cerebral laterality. The sample consisted of equal number of right and left handed school children. Lateral preference inventory was used to assess the handedness and footedness.This study was aimed at the distribution, the frequencies and the correlation between the laterality of handedness, foot preference and foot overlapping.

 

 

 

INTRODUCTION:

Lateral preference refers to the asymmetrical use of paired organs such as ears, eyes, feet, hands, limbs or of sensory organs. Lateral preference in human beings is commonly assessed by means of handedness. Surprisingly, the associations between various measures of lateral preference have revolved out to be rather low¹. Different laterality measures (e.g., proximal - distal actions, skilled-unskilled actions) have been narrated². even within the researches for handedness.

 

 

Cerebral dominance plays a key role in effecting the preference in handedness³, with right-handedness most commonly associated to a dominant and stable left hemispheric control when compared to that of left-handedness or ambidexterity⁴. Despite the fact wherein handedness is deemed to be the reliable choice for predicting language dominance,recent research works often insists on the analysis of footedness and postural whole body actions⁵ which are also found to be competent parameters as that of handedness in the spheres of lateral dominance.

 

Experimental works that have been carried out to identify reliable predictors for the lateral dominance have yet to disclose a one shot perfect predictor for laterality but has exposed that handedness has received greater attention in most of the research studies despite the general concord that language laterality based on handedness alone is comparatively weak. Hence to establish cerebral dominance the parameter has to be analysed with regard to other dimensions like language lateralization⁶, lateralization of spatial abilities⁷ and lateralization of perception for emotion⁸. However, some recent studies shows that with preferred foot ,lateralization for language differs whereas it is not with hand preference⁹. Hence with the established fact that footedness decides language laterality, then its dependency on other functional asymmetries is to be studied. Most of the functions related to language are usually coordinated by the left cerebral hemisphere whereas a right-hemispheric function is seen normally in footedness.

 

Emotional behaviours and expressions are normally actuated by the right hemisphere. Provided the task of discriminating the emotional tones in conversations, patients who endure from right-hemispheric lesions would perform worse when compared to those who have injury in the left cerebral hemisphere¹⁰. Not only for emotional tones, it has also been established that patients with injury in the right cerebral hemisphere have serious impairments in identifying emotional facial expressions also, against those suffering from left hemispheric lesions¹¹.

 

Several theories have described the evolutionary relationship between footedness and cerebral lateralization. MacNeilage has proposed that specialization for cerebral hemisphere evolved in two steps; the first being the specialization involving cerebral hemisphere for the left hand, and then the visuospatial specialization by the right hemisphere for unimanual plundering. The demands of posture in unimanual predation then guide to a right side, left-hemisphere specialization for the support of posture. In the mechanism of language production, postural factors play a indispensable part in influencing the respiratory and phonatory parts of the body. As early communications are characterised mostly by facial and whole body communicative gestures, the left cerebral hemisphere would have been predisposed with semantic functions and the right cerebral hemisphere dominating for emotional behaviours and perceptions¹².

 

This research work is intended to analyse the probability of using foot preference as a valuable and reliable predictor for lateralization.

 

MATERIALS AND METHODS:

A sample of 210 student volunteers were selected from various schools for the study. They were selected in such a way,that the sample for the present study consisted of equal number of right handed and left handed volunteers. Sample selection was based on systemic random sampling method.

 

Inclusion criteria:

1. Consenting individuals both male and female between 11-17 years.

2. Consenting right handers matching to left handers were rolled in.

 

Exclusion criteria:

1.     Individuals having any gross deformity were excluded

2.     Individuals who cannot give consent to participate in the study.

 

The parents of these volunteers were informed about the intended study, its procedures and consent was also obtained from the parents of each volunteer before inclusion in this protocol, which received the approval of the Institutional Human Ethics Committee.

 

Handedness and footedness were assessed by Lateral Preference Inventory¹³ . Foot overlapping was assessed by the leg on the top position when the individuals were asked to sit with one leg crossed over the other.

 

RESULTS AND DISCUSSION:

Right handers:

Table -1 Frequency distribution for footedness in right handed females

Right handed Females		Frequency	Percent	Valid Percent	Cumulative Percent
Valid	L	4	10.3	10.3	10.3
	R	35	89.7	89.7	100.0
	Total	39	100.0	100.0

Among the right handed females right footedness predominates. 89.7% were right footed and 10.3 % were left footed

 

Table-2 Frequency distribution for footedness in right handed males

Right handed Males		Frequency	Percent	Valid Percent	Cumulative Percent
Valid	L	3	4.5	4.5	4.5
	R	63	95.5	95.5	100.0
	Total	66	100.0	100.0

Among the right handed males also right footedness predominates.95.5% were right footed and 4.5 % were left footed

 

Table -3 Footedness and Foot overlapping in right handed females - Crosstabulation

Right handed Females		Foot overlapping		Total
		L	R
Footedness	L	0	4	4
	R	12	23	35
Total		12	27	39

In foot overlapping, both left and right footed females dominated in right side.

 

Table-4 Chi-Square Tests

Right handed Females	Value	df	Asymp. Sig. (2-sided)	Exact Sig. (2-sided)	Exact Sig. (1-sided)
Pearson Chi-Square	1.981	1	.159
Continuity Correctionc	.698	1	.403
Likelihood Ratio	3.141	1	.076
Fisher's Exact Test				.292	.213
N of Valid Cases	39

 

Table-5 Footedness and Foot overlapping in right handed males Crosstabulation

Right handed Males		Foot overlapping		Total
		L	R
Footedness	L	1	2	3
	R	21	42	63
Total		22	44	66

In foot overlapping, both left and right footed males dominated in right side.

 

Table-6 Chi-Square Tests

	Value	df	Asymp. Sig. (2-sided)	Exact Sig. (2-sided)	Exact Sig. (1-sided)
Pearson Chi-Square	.000	1	1.000
Continuity Correctionc	.000	1	1.000
Likelihood Ratio	.000	1	1.000
Fisher's Exact Test				1.000	.744
N of Valid Cases	66

 

 

 

Left handers

Table -7 Frequency distribution for footedness in left handed females

Left handed Females		Frequency	Percent	Valid Percent	Cumulative Percent
Valid	L	29	74.4	74.4	74.4
	R	10	25.6	25.6	100.0
	Total	39	100.0	100.0

Among the left handed females left footedness predominates.74.4% were left footed and 25.6 % were left footed

 

Table-8 Frequency distribution for footedness in left handed males

Left handed Males		Frequency	Percent	Valid Percent	Cumulative Percent
Valid	L	47	71.2	71.2	71.2
	R	19	28.8	28.8	100.0
	Total	66	100.0	100.0

Among the left handed males also left footedness predominates.71.2% were left footed and 28.8 % were right footed

 

Table-9 Footedness and Foot overlapping in left handed females - Crosstabulation

Left handed Females		Foot overlapping		Total
		L	R
Footedness	L	21	8	29
	R	8	2	10
Total		29	10	39

 

In foot overlapping, both left and right footed females dominated in left side

 

Table-10 Chi-Square Tests

Left handed Females	Value	df	Asymp. Sig. (2-sided)	Exact Sig. (2-sided)	Exact Sig. (1-sided)
Pearson Chi-Square	.224b	1	.636
Continuity Correctionc	.003	1	.957
Likelihood Ratio	.233	1	.629
Fisher's Exact Test				1.000	.493
N of Valid Cases	39

 

Table-11 Footedness and Foot overlapping in left handed males-Crosstabulation

Left handed Males		Foot overlapping		Total
		L	R
Footedness	L	35	12	47
	R	15	4	19
Total		50	16	66

In foot overlapping, both left and right footed males dominated in left side

 

Table–12 Chi-Square Tests

Left handers	Value	df	Asymp. Sig. (2-sided)	Exact Sig. (2-sided)	Exact Sig. (1-sided)
Pearson Chi-Square	.148b	1	.701
Continuity Correctionc	.005	1	.946
Likelihood Ratio	.151	1	.698
Fisher's Exact Test				1.000	.483
N of Valid Cases	66

 

Generally, studies in visual field as well as dichotic listening implicates the emotional perceptions and stimuli from the right cerebral hemisphere. A study of cerebral laterality associated with emotions on patients who had brain damage unilaterally reveals that, right cerebral hemisphere is associated more with negative emotions, whereas positive emotions are produced by the left cerebral hemisphere. Also patients with injury in the left-cerebral hemisphere are more prone to develop post injury depression than right-hemispheric lesioned patients¹⁴. Moreover, right-hemispheric lesions affects positive mood and even pathological laughter, whereas neagtive mood changes are induced by left hemispheric lesions, such as an increase in crying ¹⁵. Hence, to identify the potential predictor factor among handedness an footedness in characterising the lateral behavior for emotional perceptions, the individuals under test should incongruent hand as well as foot preferences. Research papers says that most of the people showed uncrossed lateral preferences, that is,the preferred foot is of the same side to the preferred hand. However, between 1.5% and 6% of right-handed adults appear to prefer their left foot. In left handed subjects the commonness of crossed lateral preference is quite higher, in which about 20% to 50% of left handers favour their right foot ¹⁶.

 

Theoretical concepts claims that similar motor activities are involved for semantic functions and prime manual skills, thereby demanding that these functionalities to be confined to the same cerebral hemisphere. While presuming that other functions like visuospatial skills and emotional perception were lateralized to the right hemisphere. Therfore, in the event of fine manual skills more likely to be attributed to cerebral lateralization, then it appears that handedness should predict language lateralization more accurately than footedness¹⁷

 

Some research works proposed that pathological events during the advanced phases of neurodevelopment leads to brain abnormalities in schizophrenia ¹⁸, which could be the reason for the corporation between incongruent laterality patterns and psychiatric traits¹⁹. In this regard, callosal morphology is declared to be the anatomical base for the diminished function of hemispheric asymmetries²⁰. But the attribute to this improper function of hemispherical asymmetries whether being relative lack or a relative surplus of fibers is a question. Some researches however have marked that a larger corpus callosum was found in left handers when compared with its counterpart ²¹

 

CONCLUSION:

Left handed people living in a dominant right handed world have to eventually adapt to the right handed facilitating equipments and infrastructures in schools, workplaces and day to day activities. This may influence the handedness behaviour to get established to the right handed aspects of performing works, but cannot influence the behavior of foot preferences. Therefore, footedness can be considered as authentic and equivalent measure to handedness as impact of culture and environment have less effect on foot preference based cerebral lateralization when compared to handedness criteria. Moreover,this could explain why a fraction of the right-handed population is left-footed.

 

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Accepted on 08.10.2018           © RJPT All right reserved

Research J. Pharm. and Tech 2018; 11(11): 5101-5104.