Null cross-modal effects of olfactory training on visual, auditory or olfactory working memory in 6- to 9-year-old children

Figures & data

Figure 1. Distribution of the parent-reported compliance with OT across each group. The dashed line depicts the inclusion cut-off of 50%. OT = olfactory training.

Two boxplots and raw-data points presenting distribution of the parent-reported compliance with olfactory training across children in the olfactory training and placebo groups. At the level of 50% compliance, there is a dashed line presenting the cut-off point for inclusion of participants in the analyses. The distribution does not differ between the two study groups, approximately 25% of participants scored below the cut-off line.

Figure 2. Flowchart presenting the number of participants who completed each part of the study. OT = olfactory training, WM = working memory.

Read the detailed description of this figure

130 participants were invited for the baseline appointment. Of these, 64 were girls. These participants have been assigned to the olfactory training group (76 participants, of these 36 girls) or the placebo group (54 participants, of these 27 girls). Before the second appointment 15 participants (9 girls) dropped out from the olfactory training group and 10 participants (1 girl) dropped out from the placebo group. 61 children (27 girls) finished the study in the olfactory training group, and 44 children (26 girls) finished the study in the placebo group. Based on compliance with the olfactory training or hyposmia, 15 children (8 girls) were excluded from the olfactory training group, and 6 children (5 girls) were excluded from the placebo group. The final number of participants in each of the working memory tasks: in the olfactory training group – 19 children (5 girls) for the olfactory memory, 45 children (19 girls) for the visual memory, 46 children (19 girls) for the auditory memory; in the placebo group: 27 children (14 girls) for the olfactory memory, 37 children (20 girls) for the visual memory, and 38 children (21 girls) for the auditory memory.

Table 1. Odours used in the olfactory working memory task.

Set A	Set B
Orange^1	Grapefruit^5
Strawberry^2	Raspberry^1
Peppermint^3	Spearmint^4
Jasmine^4	Lavender^1
Linen^4	Soap^4
Vanilla^4	Coconut^6

Note. Manufacturer: 1 – Frey + Lau; 2 – Systema Natura; 3 – Accords & Parfums; 4 – Takasago; 5 – Primavera Life–Gmbh; and 6 – biOrigins.

Table 2. Three sets of Polish words used in the auditory working memory task (English word in brackets).

Set A	talerz (a plate), pies (a dog), lampa (a lamp), list (a letter), jabłko (an apple), spodnie (trousers), stół (a table), łąka (a meadow), szklanka (a glass), and drzewo (a tree)
Set B	krzesło (a chair), kot (a cat), okno (a window), but (a shoe), banan (a banana), bluzka (a blouse), nóż (a knife), mucha (a fly), kubek (a mug), and ławka (a bench)
Set C	kamień (a stone), koń (a horse), półka (a shelf), chleb (a bread), gruszka (a pear), majtki (briefs), nos (a nose), komar (a mosquito), miska (a bowl), and trawa (grass)

Table 3. Estimated marginal means of the working memory scores across the sensory domains presented by group, while controlling for age.

Memory assessed	Olfactory training group			Placebo group
	Pre-training M (SE)	Post-training M (SE)	n	Pre-training M (SE)	Post-training M (SE)	n
Olfactory	25.5 (1.76)	25.3 (2.98)	19	26.3 (1.48)	31.8 (2.50)	27
Visual	42.1 (2.16)	42.3 (1.96)	45	40 (2.09)	39.6 (2.16)	37
Auditory – immediate	10.2 (.42)	11.3 (.44)	46	10.9 (.46)	12.1 (.49)	38
Auditory – delayed	4.67 (.35)	5.01 (.30)	46	5.24 (.39)	5.88 (.33)	38

Note. M – estimated marginal mean; SE – standard error.

Figure 3. Scores on the olfactory (panel A) and visual (panel B) working memory tests during pre- and post-training by olfactory training and placebo groups. The scores indicate the number of moves required to finish the task where lower scores indicate better performance. Mean scores are represented by the horizontal line in the violin plots.

Violin plots and boxplots plots presented with data points, presented separately for the olfactory training and placebo groups at pre- and post-training appointments. In panel A, scores in olfactory working memory are presented on the Y-axis. In panel B, scores in visual working memory are presented on the Y-axis. Distributions of the sores are overlapping between groups and across time, showing that there was no significant change in the olfactory and visual working memory across time, in any of the study groups.

Figure 4. Scores in auditory working memory task for immediate (panel A) and delayed (panel B) recall of a list of words during pre- and post-training assessment in the olfactory training and placebo groups. Mean scores are represented by the longer line in the middle of violin plots.

Violin plots and boxplots plots presented with data points, presented separately for the olfactory training and placebo groups at pre- and post-training appointments. In panel A, scores in immediate auditory working memory are presented on the Y-axis. In panel B, scores in delayed auditory working memory are presented on the Y-axis. Distributions of the sores are overlapping between groups and across time, showing that there was no significant change in the olfactory and visual working memory across time, in any of the study groups.

Data availability statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.