. 2019 May 3;7:e6833. doi: 10.7717/peerj.6833

Table 2. Effect of the additional tasks relative to baseline conditions on regional cortical activation in healthy young adults, healthy older adults and clinical groups with balance disorders.

	Healthy young adults	Healthy older adults	Clinical groups with balance disorders
Simple walking
Caliandro et al. (2015)^a		PFC (=)	PFC (+)^k
Lin & Lin (2016)^a	PFC (+)
Hawkins et al. (2018)^a	PFC (−)	PFC (+)^d, PFC (=)^e	PFC (+)^d^,^l, PFC (=)^e^,^l
Thumm et al. (2018)^a			PFC (+)^m
Fast walking
Harada et al. (2009)^a		left PFC (+), right PFC (=), preSMA (=), SMA (+), mSMC (=)
Eggenberger et al. (2016)^b		PFC (=)
Suzuki et al. (2004)^b	PFC (+), PMC (=), SMC (=)
Motor task
Chen et al. (2017)^b		PFC (+)^f
Clark et al. (2014b)^b		PFC (+)^f
Koenraadt et al. (2014)^b	PFC (−)^d, PFC (=)^e, preSMA (=), SMA (=), S1 (=), M1 (=)
Lin & Lin (2016)^a	PFC (−)
Lu et al. (2015)^b	left PFC (+), SMA (+)
Maidan et al. (2016)^b		PFC (=)	PFC (+)^m
Maidan et al. (2018)^b	PFC (+)
Mirelman et al. (2017)^b	PFC (+)	PFC (+)
Osofundiya et al. (2016)^a^,^b		PFC (+)	PFC (+)ⁿ
Hawkins et al. (2018)^a	PFC (−)	PFC (=)	PFC (+)^l
Somatosensory task
Chaparro et al. (2017)^a^,^c		PFC (+)	PFC (+)^o
Clark et al. (2014a)^b		PFC (−)
Clark et al. (2014b)^b		PFC (=)
Cognitive task
Al-Yahya et al. (2016)^b		PFC (=)	PFC (+)^l
Beurskens et al. (2014)^b	PFC (=)	PFC (−)^g, PFC (=)^h
Chaparro et al. (2017)^a^,^c		PFC (+)	PFC (+)^o
Chen et al. (2017)^b		PFC (+)
Clark et al. (2014a)^b		PFC (+)ⁱ
Clark et al. (2014b)^b		PFC (+)
Doi et al. (2013)^b			PFC (+)^p
Hernandez et al. (2016)^b		PFC (+)	PFC (+)^o
Hill et al. (2013)^c	left PFC (+)
Hawkins et al. (2018)^a	PFC (=)	PFC (+)^d, PFC (=)^e	PFC (+)^l
Holtzer et al. (2011)^b	PFC (+)	PFC (+)
Holtzer et al. (2015)^b		PFC (+)
Holtzer et al. (2016)^b		PFC (+)	PFC (+)^q
Holtzer et al. (2017a)^b		PFC (+)
Holtzer et al. (2017b)^b		PFC (+)
Lin & Lin (2016)^a	PFC (−)
Lu et al. (2015)^b	PFC (+), PMC (+), SMA (+)
Lucas et al. (2018)^b		PFC (+)
Maidan et al. (2016)^b		PFC (+)	PFC (=)^m
Meester et al. (2014)^b	right PFC (+)
Mirelman et al. (2014)^b	PFC (+)^j
Mirelman et al. (2017)^b	PFC (+)	PFC (+)
Mori, Takeuchi & Izumi (2018)^a^,^b		PFC (=)	PFC (=)^l
Nieuwhof et al. (2016)^a			PFC (+)^m
Osofundiya et al. (2016)^a^,^b		PFC (+)	PFC (+)ⁿ
Takeuchi et al. (2016)^a	PFC (=)	PFC (=)
Verghese et al. (2017)^a		PFC (+)

Notes.

PFC: Prefrontal cortex
preSMA: Pre-supplementary motor area
SMA: Supplementary motor area
S1: Primary sensorimotor cortex
M1: Primary motor cortex
PMC: Premotor cortex
mSMC: Medial sensorimotor cortex
(+): higher activation when performing the additional task
(−): lower activation when performing the additional task
(=): no changes in activation

Baseline comparison:

Standing still.

Simple walking.

Easier level of the secondary task.

Significant differences only for:

First half of the task.

Second half of the task.

Obstacle negotiation and wearing a vest with 10% body weight conditions.

Walk vs. visual task.

Walk vs alphabet recall.

ⁱ

Overground walking.

Walking and counting backwards task.

Clinical groups:

Ataxia.

Stroke.

Parkinson’s disease.

ⁿ

Obesity.

Multiple Sclerosis.

Mild Cognitive Impairment.

Neurological gait.