Illustration of the patient data on the samples utilized

(A) Illustration of the defined age groups.

(B) Number of patients involved in age groups, (n = 6, 6, 7, 12, 22, 22, 33 from infant to late adulthood, respectively). Dots show the number of human layer 2/3 pyramidal cells in our dataset regarding the defined age groups (n = 73, 32, 48, 60, 92, 62, 118 from infant to late adulthood, respectively).

(C) Distributions of patient ages within age groups.

(D) Brain model indicates the number of surgically removed tissues from the cortical lobes. Colors indicate age groups.

(E) The distribution of recovered cell bodies distance from the L1/2 border.

Subthreshold membrane properties vary across life stage

(A-D), Boxplots show resting membrane potential (A), input resistance (B), tau (C), and sag ratio

(D) distributions in various age groups. (B) Inset shows representative voltage traces from each group. Scale bar: 5 mV; 20 ms. Asterisks indicate significance (Kruskal–Wallis test with post-hoc Dunn test, * P < 0.05, ** P < 0.01, *** P < 0.001).

Age related differences in the action potential kinetics.

(A-C) Boxplots show differences in rheobase (A), action potential half-width (B), action potential up-stroke (C), and action potential amplitude (D) between the age groups. Asterisks indicate statistical significance (* P < 0.05, ** P < 0.01, *** P < 0.001).

(E) Representative action potentials aligned to threshold potential onset (scale: x axis: 1ms, y axis: 20 mV) (top) and phase plots of the representative APs (scale: x axis: 10 mV, y axis: 100 mV/ms) (bottom).

(F) Uniform Manifold Approximation and Projection (UMAP) of 32 (top) and 8 selected electrophysiological properties (resting Vm, input resistance, tau, sag ratio, rheobase, AP half-width, AP up-stroke and AP amplitude) (bottom) with data points for 331 cortical L2/3 pyramidal cells, colored with the corresponding age groups.

Age-dependency of the AP firing pattern parameters

(A) Representative membrane potential responses to an 800 ms long rheobase (middle) (left to right: infant, early childhood, late childhood, adolescence, young adulthood, middle adulthood, late adulthood), and increased current steps (bottom) Colored respectively to the age groups. Scale bar top: 1ms, 100 pA, bottom: 1ms, 20mV.

(B-D) Boxplots show changes across the age groups in f-I slope (B), first AP latency (C), and adaptation of APs (D). Asterisks indicate statistical significance (* P < 0.05, ** P < 0.01, *** P < 0.001).

Morphological features of layer 2/3 pyramidal cells in different stages of life

(A) Representative reconstructions of L2/3 pyramidal cells (from left to right) from infant (n = 6), early childhood (n = 6), late childhood (n = 8), adolescence (n = 8), young adulthood (n = 5), middle adulthood (n = 6), and late adulthood (n = 6) patients.

(B-I) Boxplots show summarized data from all the reconstructed cells (Suppl. fig. 8) of total dendritic length (B), apical dendritic length (C), total basal dendritic length (D), the total number of nodes on the apical and basal dendrites (E), the maximal horizontal (F), and the maximal vertical (G) extension of dendrites, the average length of the apical (H) and basal (I) terminal dendritic segments.

Comparison of the number of dendritic spines between an infant and a late adulthood aged sample

(A) Anatomical 3D reconstruction of human L2/3 pyramidal cells from the infant (left), and the late adulthood (right) age groups.

(B) Boxplots of the spine densities on the apical (top), and basal (bottom) dendritic branches from the infant (blue) and late adulthood (red) L2/3 pyramidal cells shown on panel (A).

(C) Graphs showing the distribution of dendritic spine density as a function of the branch order, the infant pyramidal cell shown with blue, the late adulthood pyramidal cell with red, on the apical (top) and on the basal (bottom) dendrites.

(D-H) The plots show the distribution of mushroom (D), thin (E), filopodium (F), branched (G), and stubby (H) dendritic spine types on the apical dendrites of the reconstructed infant (blue) and late adult (cell) pyramidal cells. Top, schematic representation of the examined dendritic spine types. Center, age dependent distribution of spine types. Bottom, spine distributions along branch orders. Asterisks indicate significance (* P < 0.05, ** P < 0.01, *** P < 0.001)

(I-M) Same as D-H but on basal dendrites.